N-CSR

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number 811-09333

Oppenheimer Main Street Small- & Mid- Cap Fund

(Exact name of registrant as specified in charter)

6803 South Tucson Way, Centennial, Colorado 80112-3924

(Address of principal executive offices) (Zip code)

Arthur S. Gabinet

OFI Global Asset Management, Inc.

Two World Financial Center, New York, New York 10281-1008

(Name and address of agent for service)

Registrant’s telephone number, including area code: (303) 768-3200

Date of fiscal year end: June 30

Date of reporting period: 6/30/2013

Item 1. Reports to Stockholders.

Table of Contents

Fund Performance Discussion	3
Top Holdings and Allocations	7
Fund Expenses	10
Statement of Investments	12
Statement of Assets and Liabilities	15
Statement of Operations	17
Statements of Changes in Net Assets	18
Financial Highlights	19
Notes to Financial Statements	25
Report of Independent Registered Public Accounting Firm	38
Federal Income Tax Information	39
Portfolio Proxy Voting Policies and Procedures; Updates to Statement of Investments	40
Trustees and Officers	41
Privacy Policy Notice	49

Class A Shares

AVERAGE ANNUAL TOTAL RETURNS AT 6/28/13

	Class A Shares of the Fund
	Without Sales Charge		With Sales Charge		Russell 2500 Index
1-Year		21.30%		14.33%		25.61%
5-Year		8.26		6.98		9.21
10-Year		9.61		8.96		10.34

Performance data quoted represents past performance, which does not guarantee future results.  The investment return and principal value of an investment in the Fund will fluctuate so that an investor’s shares, when redeemed, may be worth more or less than their original cost. Fund returns include changes in share price, reinvested distributions, and a 5.75% maximum applicable sales charge except where “without sales charge” is indicated. Returns do not consider capital gains or income taxes on an individual’s investment. For performance data current to the most recent month-end, visit oppenheimerfunds.com or call 1.800.CALL OPP (225.5677).

June 28, 2013, was the last business day of the Fund’s fiscal year. See Note 1 of the accompanying Notes to Financial Statements. Index returns are calculated through June 30, 2013.

2      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Fund Performance Discussion

The Fund’s Class A shares (without sales charge) produced a total return of 21.30%, underperforming the Russell 2500 Index (the “Index”), which returned 25.61%. The Fund’s underperformance relative to the Index stemmed primarily from weaker relative stock selection in the financials, consumer discretionary and information technology sectors. The Fund outperformed the Index in the materials and energy sectors, where favorable stock selection benefited.

MARKET OVERVIEW

Central banks throughout the world announced new accommodative policy measures intended to promote market liquidity and stimulate greater economic growth. In September 2012, the U.S. Federal Reserve (the “Fed”) embarked on a new round of open-ended quantitative easing involving monthly purchases of mortgage-backed securities issued by U.S. government agencies, also known as “QE3”. In addition to the Fed’s measures, the U.S. housing market continued to improve and Gross

Domestic Product maintained a moderate rate of growth. Meanwhile, outside the U.S., the head of the European Central Bank (the “ECB”) had reassured investors that the ECB was committed to supporting the Eurozone, and the ECB signaled its conditional intention to purchase massive amounts of debt from troubled members of the European Union. Even in Japan, which had been mired in economic weakness for years, new government leadership adopted economic policies and the central bank announced a

COMPARISON OF CHANGE IN VALUE OF $10,000 HYPOTHETICAL INVESTMENTS IN:

3      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

massive quantitative easing program. Investors reacted positively to these measures and markets rallied for most of the reporting period.

However, towards the end of the period, the Fed appeared to weigh the merits of backing away from its quantitative easing policy. As a result, the markets sold off sharply and made a quick reappraisal of interest rate risk in an array of credit markets and related currencies. Equities, particularly those in emerging markets and in interest rate sensitive sectors, experienced spillover effects as a result.

FUND REVIEW

During the period, the Fund’s strongest performing holdings were Western Digital Corp. and Actavis, Inc. Western Digital, which develops and sells hard drives, performed positively despite an ongoing challenging market for PC sales. As the hard disk drive industry has consolidated, the market has become more rational and improved pricing discipline has ensued – benefiting the profitability of competitors such as Western Digital. Earnings per share for the company have also been augmented by management’s decision to devote a substantial portion of the free cash generated to repurchasing shares. Actavis is a branded and generic drug company that spiked when management announced it was combining operations with Warner Chilcott – a leading specialty pharmaceutical company based in Ireland. The combination has a strong strategic rationale. The merged entity is expected to benefit from revenue synergies, with

complementary product lines, and cost rationalization – both of which are expected to contribute to rising profits.

Also among the top performing stocks for the Fund were PVH Corp., Ocwen Financial Corp. and Waste Connections, Inc. PVH is a global apparel manufacturer that performed positively, as its recent acquisition of Warnaco began to benefit both top and bottom line growth. The Tommy Hilfiger brand continued its momentum in North America, and now that PVH management has control of the Calvin Klein brand, it too, is expected to realize improving revenue growth. Additionally, both brands have an opportunity to gain further share outside the U.S. market. Ocwen Financial services residential and commercial mortgages for third parties. The company’s stock performed positively in the midst of an improving housing market. Waste Connections is a provider of solid waste disposal and recycling services. Volume declines appeared to be moderating, reflecting, in part, an improving housing market. Additionally, free cash generation remains strong. The company has recently entered the energy waste business through an acquisition. This newly acquired division is beginning to bear fruit and is expected to ramp further as the year progresses – which could lead to accelerated growth.

The most significant detractors from performance this period were TIBCO Software, Inc., Questcor Pharmaceuticals, Inc. and Joy Global, Inc. Macroeconomic

4      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

headwinds, resulting in sluggish business spending, negatively impacted the progression and timing of sales for many software companies during the period, including TIBCO. We have seen from similar enterprise software companies’ results that the information technology spending environment is challenged. While we believe TIBCO remains well positioned for secular growth in the big data and analytics sectors, we have lessened our exposure to this stock. Questcor traded lower over the first half of the period as a result of market concerns involving Aetna, Inc.’s reimbursement criteria for Questcor’s drug Acthar and a probe into Questcor’s promotional practices. In the closing months of the period, its stock saw improved performance. The stock of Joy Global, a manufacturer and servicer of mining equipment, suffered from declining expectations. As commodity demand growth and prices have fallen worldwide, mining companies have pulled back on purchases of new mining equipment hurting Joy Global’s revenue and earnings outlook. The company’s aftermarket sales have helped to offset disappointing demand of original equipment as the aftermarket is more resilient during cycle downturns and tends to have higher profit margins. We believe Joy Global is well positioned to benefit as demand for commodities improves and mining companies regain confidence in the outlook for greater global growth.

STRATEGY & OUTLOOK

We believe the Fed is acting appropriately by signaling that eventually it will lessen its

monetary support of our expanding economy. While the market declined after the Fed’s comments, what seemed to be missing from the market’s response was the realization that when rates do rise, this should be a reflection of a strong economy. And this, in combination with the likelihood, in our view, that the Fed will be “tapering” later than currently feared, has set-up a potentially attractive investment opportunity in domestic equities. Company fundamentals are better positioned than at prior nominal highs in the market. And, as has been well documented throughout this tepid recovery, corporations have been very cautious about spending money – largely reflecting uncertainty about the economic and political outlook. This cautious behavior has resulted in a massive build-up of cash on corporate balance sheets which has greatly improved the fundamental health of many companies. As the economy improves and managements’ uncertainty lifts, these cash balances have the potential to be used in a constructive manner which may support rising equity valuations.

Domestically, housing has momentum and job creation, while not robust, at least continues. We expect that company fundamentals, too, will continue to show improvement – especially as companies tap into the large cash reserves that have been built-up. These factors have the potential to drive equity prices higher; however, rarely does the market appreciate on a straight upward trajectory. While we are not predicting a market correction, we do believe

5      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

that the market may return to experiencing greater volatility.

Given this backdrop, our approach remains consistent. We aim to construct an “all weather” portfolio by targeting companies that we believe have: 1) sustainable competitive advantages; 2) skilled management with a proven track record of executing effectively; and 3) financial resources to generate improving profitability, gain market share, and/or return significant capital to shareholders. During volatile economic times such companies often widen

their lead over weaker competitors. We seek to invest in companies, characterized by these qualities, at compelling valuations and believe this disciplined approach is essential.

Raymond Anello, CFA Portfolio Manager

Raymond Anello, CFA and Lead Portfolio Manager, on behalf of the Portfolio Management team: Matthew P. Ziehl, CFA, Raman Vardharaj, CFA, Joy Budzinski, Kristin Ketner Pak, Magnus Krantz and Adam Weiner.

6      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Top Holdings and Allocations*

TOP TEN COMMON STOCK HOLDINGS

Discover Financial Services	3.5%
National Oilwell Varco, Inc.	3.3
Digital Realty Trust, Inc.	3.2
Robert Half International, Inc.	3.1
Actavis, Inc.	3.0
Joy Global, Inc.	2.5
Fidelity National Financial, Inc., Cl. A	2.5
PVH Corp.	2.3
Imax Corp.	2.3
Dana Holding Corp.	2.2
Portfolio holdings and allocations are subject to change. Percentages are as of June 28, 2013, and are based on net assets. For more current Fund holdings, please visit oppenheimerfunds.com.

TOP TEN COMMON STOCK INDUSTRIES

Real Estate Investment Trusts (REITs)	7.4%
Insurance	5.8
Oil, Gas & Consumable Fuels	5.5
Machinery	5.4
Pharmaceuticals	5.3
Commercial Banks	4.7
Specialty Retail	4.0
Health Care Providers & Services	3.8
Media	3.8
Professional Services	3.8
Portfolio holdings and allocations are subject to change. Percentages are as of June 28, 2013, and are based on net assets.

SECTOR ALLOCATION

Portfolio holdings and allocations are subject to change. Percentages are as of June 28, 2013, and are based on the total market value of common stocks.

* June 28, 2013, was the last business day of the Fund’s fiscal year. See Note 1 of the accompanying Notes to Financial Statements.

7      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Share Class Performance

AVERAGE ANNUAL TOTAL RETURNS WITHOUT SALES CHARGE AS OF 6/28/13

	Inception Date		1-Year			5-Year		10-Year
Class A (OPMSX)		8/2/99		21.30%			8.26%		9.61%
Class B (OPMBX)		8/2/99		20.26%			7.38%		9.11%
Class C (OPMCX)		8/2/99		20.39%			7.44%		8.81%
Class I (OPMIX)		10/26/12		19.65%	*		N/A		N/A
Class N (OPMNX)		3/1/01		20.94%			7.97%		9.29%
Class Y (OPMYX)		8/2/99		21.74%			8.67%		10.08%

AVERAGE ANNUAL TOTAL RETURNS WITH SALES CHARGE AS OF 6/28/13

	Inception Date		1-Year			5-Year		10-Year
Class A (OPMSX)		8/2/99		14.33%			6.98%		8.96%
Class B (OPMBX)		8/2/99		15.26%			7.07%		9.11%
Class C (OPMCX)		8/2/99		19.39%			7.44%		8.81%
Class I (OPMIX)		10/26/12		19.65%	*		N/A		N/A
Class N (OPMNX)		3/1/01		19.94%			7.97%		9.29%
Class Y (OPMYX)		8/2/99		21.74%			8.67%		10.08%

*Shows performance since inception.

Performance data quoted represents past performance, which does not guarantee future results. The investment return and principal value of an investment in the Fund will fluctuate so that an investor’s shares, when redeemed, may be worth more or less than their original cost. Current performance may be lower or higher than the performance quoted. Returns do not consider capital gains or income taxes on an individual’s investment. For performance data current to the most recent month-end, visit oppenheimerfunds.com or call 1.800.CALL OPP (225.5677). Fund returns include changes in share price, reinvested distributions, and the applicable sales charge: for Class A shares, the current maximum initial sales charge of 5.75%; for Class B shares, the contingent deferred sales charge of 5% (1-year) and 2% (5-year); and for Class C and N shares, the 1% contingent deferred sales charge for the 1-year period. There is no sales charge for Class I and Class Y shares. Because Class B shares convert to Class A shares 72 months after purchase, 10-year returns for Class B shares reflect Class A performance for the period after conversion. Returns for periods of less than one year are cumulative and not annualized.

The Fund’s performance is compared to the performance of the Russell 2500 Index, a broad-based index featuring 2,500 stocks that cover the small- and mid-cap market capitalizations. The Index is unmanaged and cannot be purchased directly by investors. Index performance includes reinvestment of income, but does not reflect transaction costs, fees, expenses or taxes. Index performance is shown for illustrative purposes only as a benchmark for the Fund’s performance, and does not predict or depict performance of the Fund. The Fund’s performance reflects the effects of the Fund’s business and operating expenses.

8      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

The Fund’s investment strategy and focus can change over time. The mention of specific fund holdings does not constitute a recommendation by OppenheimerFunds, Inc. or its affiliates.

Before investing in any of the Oppenheimer funds, investors should carefully consider a fund’s investment objectives, risks, charges and expenses. Fund prospectuses and summary prospectuses contain this and other information about the funds, and may be obtained by asking your financial advisor, visiting oppenheimerfunds.com, or calling 1.800.CALL OPP (225.5677). Read prospectuses and summary prospectuses carefully before investing.

Shares of Oppenheimer funds are not deposits or obligations of any bank, are not guaranteed by any bank, are not insured by the FDIC or any other agency, and involve investment risks, including the possible loss of the principal amount invested.

9      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Fund Expenses

Fund Expenses. As a shareholder of the Fund, you incur two types of costs: (1) transaction costs, which may include sales charges (loads) on purchase payments, contingent deferred sales charges on redemptions; and (2) ongoing costs, including management fees; distribution and service fees; and other Fund expenses. These examples are intended to help you understand your ongoing costs (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds.

The examples are based on an investment of $1,000.00 invested at the beginning of the period and held for the entire 6-month period ended June 28, 2013.

Actual Expenses. The first section of the table provides information about actual account values and actual expenses. You may use the information in this section for the class of shares you hold, together with the amount you invested, to estimate the expense that you paid over the period. Simply divide your account value by $1,000.00 (for example, an $8,600.00 account value divided by $1,000.00 = 8.60), then multiply the result by the number in the first section under the heading entitled “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes. The second section of the table provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratio for each class of shares, and an assumed rate of return of 5% per year for each class before expenses, which is not the actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example for the class of shares you hold with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transactional costs, such as front-end or contingent deferred sales charges (loads), or a $12.00 fee imposed annually on accounts valued at less than $500.00 (subject to exceptions described in the Statement of Additional Information). Therefore, the “hypothetical” section of the table is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds. In addition, if these transactional costs were included, your costs would have been higher.

10      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Actual	Beginning Account Value January 1, 2013		Ending Account Value June 28, 2013		Expenses Paid During 6 Months Ended June 28, 2013
Class A	$	1,000.00	$	1,138.80	$	6.15
Class B		1,000.00		1,134.20		10.51
Class C		1,000.00		1,134.40		10.04
Class I		1,000.00		1,141.90		3.47
Class N		1,000.00		1,137.30		7.73
Class Y		1,000.00		1,140.90		4.15
Hypothetical (5% return before expenses)
Class A		1,000.00		1,018.78		5.81
Class B		1,000.00		1,014.71		9.93
Class C		1,000.00		1,015.15		9.48
Class I		1,000.00		1,021.28		3.28
Class N		1,000.00		1,017.31		7.30
Class Y		1,000.00		1,020.65		3.92
Expenses are equal to the Fund’s annualized expense ratio for that class, multiplied by the average account value over the period, multiplied by 179/365 (to reflect the one-half year period). Those annualized expense ratios, excluding indirect expenses from affiliated funds, based on the 6-month period ended June 28, 2013 are as follows:

Class	Expense Ratios
Class A		1.17%
Class B		2.00
Class C		1.91
Class I		0.66
Class N		1.47
Class Y		0.79

The expense ratios reflect voluntary waivers and/or reimbursements of expenses by the Fund’s Manager and Transfer Agent. Some of these undertakings may be modified or terminated at any time, as indicated in the Fund’s prospectus. The “Financial Highlights” tables in the Fund’s financial statements, included in this report, also show the gross expense ratios, without such waivers or reimbursements and reduction to custodian expenses, if applicable.

11      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

STATEMENT OF INVESTMENTS    June 28, 2013*

	Shares		Value
Common Stocks—98.6%
Consumer Discretionary—16.0%
Auto Components—2.2%
Dana Holding Corp.		3,980,223	$	76,659,095
Hotels, Restaurants & Leisure—1.3%
Dunkin’ Brands Group, Inc.		651,275		27,887,596
Norwegian Cruise Line Holdings Ltd.1		586,540		17,778,027
				45,665,623
Household Durables—0.8%
Toll Brothers, Inc.1		888,319		28,985,849
Internet & Catalog Retail—0.5%
Expedia, Inc.		297,480		17,893,422
Media—3.8%
AMC Networks, Inc., Cl. A1		819,870		53,627,697
Imax Corp.1		3,177,633		78,995,956
				132,623,653
Specialty Retail—4.0%
O’Reilly Automotive, Inc.1		542,510		61,097,476
Pier 1 Imports, Inc.		1,093,383		25,683,567
Ross Stores, Inc.		833,930		54,047,003
				140,828,046
Textiles, Apparel & Luxury Goods—3.4%
Fossil Group, Inc.1		368,461		38,065,706
PVH Corp.		639,011		79,908,325
				117,974,031
Consumer Staples—2.9%
Food Products—1.9%
Flowers Foods, Inc.		3,005,160		66,263,778
Personal Products—1.0%
Nu Skin Enterprises, Inc., Cl. A		580,320		35,469,158
Energy—8.8%
Energy Equipment & Services—3.3%
National Oilwell Varco, Inc.		1,668,760		114,977,564
Oil, Gas & Consumable Fuels—5.5%
CVR Energy, Inc., Escrow Shares1,2		155,957		—
HollyFrontier Corp.		626,155		26,786,911
Noble Energy, Inc.		765,480		45,959,419
PAA Natural Gas Storage LP		930,353		19,574,627
QEP Resources, Inc.		2,608,070		72,452,185
Western Refining, Inc.		931,710		26,153,100
				190,926,242
Financials—24.9%
Commercial Banks—4.7%
CapitalSource, Inc.		3,759,110		35,260,452

	Shares		Value
Commercial Banks (Continued)
Comerica, Inc.		651,110	$	25,933,711
Commerce Bancshares, Inc.		792,810		34,534,804
Huntington Bancshares, Inc.		8,474,663		66,780,344
				162,509,311
Consumer Finance—3.5%
Discover Financial Services		2,547,580		121,366,711
Diversified Financial Services—0.6%
Moody’s Corp.		340,809		20,765,492
Insurance—5.8%
AmTrust Financial Services, Inc.		836,420		29,860,194
Fidelity National Financial, Inc., Cl. A		3,600,280		85,722,667
Lincoln National Corp.		1,608,110		58,647,772
Willis Group Holdings plc		665,040		27,120,331
				201,350,964
Real Estate Investment Trusts (REITs)—7.4%
Digital Realty Trust, Inc.		1,856,253		113,231,433
Hatteras Financial Corp.		1,848,059		45,536,174
Mid-America Apartment Communities, Inc.		318,550		21,588,133
Redwood Trust, Inc.		1,781,730		30,289,410
Starwood Property Trust, Inc.		1,925,996		47,668,401
				258,313,551
Thrifts & Mortgage Finance—2.9%
Home Loan Servicing Solutions Ltd.		760,030		18,217,919
Ocwen Financial Corp.1		1,366,510		56,327,542
People’s United Financial, Inc.		1,726,250		25,721,125
				100,266,586
Health Care—12.9%
Biotechnology—1.3%
Medivation, Inc.1		469,188		23,084,050
Onyx Pharmaceuticals, Inc.1		245,000		21,270,900
				44,354,950
Health Care Equipment & Supplies—2.5%
CareFusion Corp.1		789,860		29,106,341
Cooper Cos., Inc. (The)		276,800		32,953,040

12      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

	Shares		Value
Health Care Equipment & Supplies (Continued)
DexCom, Inc.1		1,141,961	$	25,637,024
				87,696,405
Health Care Providers & Services—3.8%
HealthSouth Corp.1		1,797,574		51,770,131
Omnicare, Inc.		1,193,253		56,930,101
Universal Health Services, Inc., Cl. B		380,300		25,464,888
				134,165,120
Pharmaceuticals—5.3%
Actavis, Inc.1		832,160		105,035,235
Questcor Pharmaceuticals, Inc.		383,017		17,411,953
Zoetis, Inc.		2,013,757		62,204,954
				184,652,142
Industrials—18.0%
Aerospace & Defense—3.1%
B/E Aerospace, Inc.1		547,361		34,527,532
L-3 Communications Holdings, Inc.		847,190		72,638,070
				107,165,602
Commercial Services & Supplies—2.2%
Waste Connections, Inc.		1,851,028		76,151,292
Construction & Engineering—1.5%
KBR, Inc.		1,598,370		51,947,025
Machinery—5.4%
AGCO Corp.		1,389,770		69,752,556
Joy Global, Inc.		1,794,789		87,101,110
Wabtec Corp.		620,344		33,144,980
				189,998,646
Professional Services—3.8%
Robert Half International, Inc.		3,286,320		109,204,414
Towers Watson & Co., Cl. A		264,980		21,712,461
				130,916,875
Road & Rail—2.0%
Old Dominion Freight Line, Inc.1		1,678,687		69,866,953
Information Technology—10.5%
Computers & Peripherals—1.2%
Western Digital Corp.		655,262		40,685,218
IT Services—2.2%
Amdocs Ltd.		727,075		26,967,212
Vantiv, Inc., Cl. A1		1,784,240		49,245,024
				76,212,236

	Shares			Value
Semiconductors & Semiconductor Equipment—3.7%
Cavium, Inc.1		1,066,470		$	37,721,044
Semtech Corp.1		542,595			19,007,103
Skyworks Solutions, Inc.1		3,367,994			73,725,388
					130,453,535
Software—3.4%
Fortinet, Inc.1		1,951,436			34,150,130
Synopsys, Inc.1		1,539,396			55,033,407
TIBCO Software, Inc.1		1,317,234			28,188,808
					117,372,345
Materials—4.1%
Chemicals—1.9%
Cytec Industries, Inc.		231,620			16,966,165
W.R. Grace & Co.1		569,192			47,834,896
					64,801,061
Containers & Packaging—1.4%
Packaging Corp. of America		1,029,952			50,426,450
Metals & Mining—0.8%
Compass Minerals International, Inc.		329,090			27,817,978
Utilities—0.5%
Water Utilities—0.5%
Aqua America, Inc.		611,114			19,121,757
Total Common Stocks (Cost $2,779,485,710)					3,436,644,666
Investment Company—2.0%
Oppenheimer Institutional Money Market Fund, Cl. E, 0.11%3,4 (Cost $68,207,347)		68,207,347			68,207,347
Total Investments, at Value (Cost $2,847,693,057)		100.6%			3,504,852,013
Liabilities in Excess of Other Assets		(0.6	)		(19,613,297)
Net Assets		100.0%		$	3,485,238,716

13      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

STATEMENT OF INVESTMENTSContinued

Footnotes to Statement of Investments

*June 28, 2013 represents the last business day of the Fund’s 2013 fiscal year. See Note 1 of the accompanying Notes.

1. Non-income producing security.

2. Escrow shares received as a result of issuer reorganization.

3. Is or was an affiliate, as defined in the Investment Company Act of 1940, at or during the period ended June 28, 2013, by virtue of the Fund owning at least 5% of the voting securities of the issuer or as a result of the Fund and the issuer having the same investment adviser. Transactions during the period in which the issuer was an affiliate are as follows:

	Shares June 29, 2012a		Gross Additions		Gross  Reductions		Shares     June 28, 2013
Oppenheimer Institutional Money Market Fund, Cl. E		65,788,312		1,161,307,196		1,158,888,161		68,207,347
Renewable Energy Group		818,930		7,515		826,445		—

	Value		Income		Realized     Loss
Oppenheimer Institutional Money Market Fund, Cl. E	$	68,207,347	$	147,199	$	—
Renewable Energy Group		—		—		2,996,346
Total	$	68,207,347	$	147,199	$	2,996,346

    a. June 29, 2012 represents the last business day of the Fund’s 2012 fiscal year. See Note 1 of the accompanying Notes.

4. Rate shown is the 7-day yield as of June 28, 2013.

See accompanying Notes to Financial Statements.

14      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

STATEMENT OF ASSETS AND LIABILITIES      _{June 28, 2013}¹

Assets
Investments, at value—see accompanying statement of investments:
Unaffiliated companies (cost $2,779,485,710)	$	3,436,644,666
Affiliated companies (cost $68,207,347)		68,207,347
		3,504,852,013
Cash		63,774
Receivables and other assets:
Investments sold		20,609,584
Dividends		4,257,695
Other		144,870
Total assets		3,529,927,936
Liabilities
Payables and other liabilities:
Investments purchased		37,753,917
Shares of beneficial interest redeemed		5,385,383
Transfer and shareholder servicing agent fees		702,519
Distribution and service plan fees		486,100
Shareholder communications		169,305
Trustees’ compensation		117,986
Other		74,010
Total liabilities		44,689,220
Net Assets	$	3,485,238,716
Composition of Net Assets
Par value of shares of beneficial interest	$	133,022
Additional paid-in capital		3,091,760,563
Accumulated net investment income		2,915,244
Accumulated net realized loss on investments		(266,729,069)
Net unrealized appreciation on investments		657,158,956
Net Assets	$	3,485,238,716

1. June 28, 2013 represents the last business day of the Fund’s 2013 fiscal year. See Note 1 of the accompanying Notes.

15      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

STATEMENT OF ASSETS AND LIABILITIES      Continued

Net Asset Value Per Share
Class A Shares:
Net asset value and redemption price per share (based on net assets of $1,716,474,622 and 65,584,126 shares of beneficial interest outstanding)	$26.17
Maximum offering price per share (net asset value plus sales charge of 5.75% of offering price)	$27.77
Class B Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $57,998,767 and 2,485,663 shares of beneficial interest outstanding)	$23.33
Class C Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $334,869,753 and 14,265,931 shares of beneficial interest outstanding)	$23.47
Class I Shares:
Net asset value, redemption price and offering price per share (based on net assets of $362,309,904 and 13,167,114 shares of beneficial interest outstanding)	$27.52
Class N Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $224,448,444 and 8,855,436 shares of beneficial interest outstanding)	$25.35
Class Y Shares:
Net asset value, redemption price and offering price per share (based on net assets of $789,137,226 and 28,663,243 shares of beneficial interest outstanding)	$27.53

See accompanying Notes to Financial Statements

16      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

STATEMENT OF OPERATIONS      _{For the Year Ended June 28, 2013}¹

Investment Income
Dividends:
Unaffiliated companies (net of foreign withholding taxes of $27,823)	$	60,405,855
Affiliated companies		147,199
Interest		1,598
Other income		38,650
Total investment income		60,593,302
Expenses
Management fees		20,860,825
Distribution and service plan fees:
Class A		4,207,281
Class B		623,062
Class C		3,252,709
Class N		1,099,747
Transfer and shareholder servicing agent fees:
Class A		4,916,226
Class B		345,205
Class C		923,431
Class I		13,502
Class N		854,360
Class Y		1,538,796
Shareholder communications:
Class A		342,247
Class B		42,157
Class C		75,456
Class I		63
Class N		20,075
Class Y		91,198
Trustees’ compensation		176,069
Custodian fees and expenses		17,330
Other		374,929
Total expenses		39,774,668
Less waivers and reimbursements of expenses		(314,109)
Net expenses		39,460,559
Net Investment Income		21,132,743
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on investments from:
Unaffiliated companies		436,851,510
Affiliated companies		(2,996,346)
Total net realized gain		433,855,164
Net change in unrealized appreciation/depreciation on investments		191,224,320
Net Increase in Net Assets Resulting from Operations	$	646,212,227

1. June 28, 2013 represents the last business day of the Fund’s 2013 fiscal year. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

17      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

STATEMENTS OF CHANGES IN NET ASSETS

	Year Ended June 28, 20131		Year Ended June 29, 20121
Operations
Net investment income	$	21,132,743	$	6,280,244
Net realized gain		433,855,164		241,491,120
Net change in unrealized appreciation/depreciation		191,224,320		(323,311,811)
Net increase (decrease) in net assets resulting from operations		646,212,227		(75,540,447)
Dividends and/or Distributions to Shareholders
Dividends from net investment income:
Class A		(13,235,886)		(3,870,465)
Class B		—		—
Class C		(553,406)		—
Class I		(137)		—
Class N		(1,089,794)		—
Class Y		(11,120,488)		(5,475,891)
		(25,999,711)		(9,346,356)
Beneficial Interest Transactions
Net increase (decrease) in net assets resulting from beneficial interest transactions:
Class A		(262,944,077)		(316,651,609)
Class B		(22,533,209)		(31,227,895)
Class C		(45,470,282)		(53,714,746)
Class I		364,066,494		—
Class N		(43,304,790)		(40,324,183)
Class Y		(312,573,152)		(131,726,021)
		(322,759,016)		(573,644,454)
Net Assets
Total increase (decrease)		297,453,500		(658,531,257)
Beginning of period		3,187,785,216		3,846,316,473
End of period (including accumulated net investment income of $2,915,244 and $5,997,772, respectively)	$	3,485,238,716	$	3,187,785,216

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective 2013 and 2012 fiscal years. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

18      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

FINANCIAL HIGHLIGHTS

Class A	Year Ended June 28, 20131		Year Ended June 29, 20121		Year Ended June 30, 2011		Year Ended June 30, 2010		Year Ended June 30, 2009
Per Share Operating Data
Net asset value, beginning of period	$	21.75	$	21.99	$	16.33	$	13.70	$	17.87
Income (loss) from investment operations:
Net investment income2		0.15		0.04		0.05		0.02		0.08
Net realized and unrealized gain (loss)		4.45		(0.23)		5.61		2.64		(4.22)
Total from investment operations		4.60		(0.19)		5.66		2.66		(4.14)
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.18)		(0.05)		0.00		(0.03)		0.00
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.03)
Total dividends and/or distributions to shareholders		(0.18)		(0.05)		0.00		(0.03)		(0.03)
Net asset value, end of period	$	26.17	$	21.75	$	21.99	$	16.33	$	13.70
Total Return, at Net Asset Value3		21.30%		(0.85)%		34.66%		19.45%		(23.14)%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	1,716,475	$	1,662,531	$	2,026,656	$	1,849,907	$	1,804,702
Average net assets (in thousands)	$	1,708,977	$	1,696,301	$	2,016,616	$	1,988,573	$	2,231,028
Ratios to average net assets:4
Net investment income		0.62%		0.20%		0.28%		0.13%		0.58%
Total expenses5		1.19%		1.24%		1.25%		1.31%		1.38%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		1.19%		1.24%		1.24%		1.25%		1.22%
Portfolio turnover rate		101 %		81 %		86 %		101 %		95 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective 2013 and 2012 fiscal years. See Note 1 of the accompanying Notes.

2. Per share amounts calculated based on the average shares outstanding during the period.

3. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

4. Annualized for periods less than one full year.

5. Total expenses including indirect expenses from affiliated fund were as follows:

Year Ended June 28, 2013	1.19	%
Year Ended June 29, 2012	1.24	%
Year Ended June 30, 2011	1.25	%
Year Ended June 30, 2010	1.31	%
Year Ended June 30, 2009	1.38	%

See accompanying Notes to Financial Statements.

19      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

FINANCIAL HIGHLIGHTS    Continued

Class B	Year Ended June 28, 20131		Year Ended June 29, 20121		Year Ended June 30, 2011		Year Ended June 30, 2010		Year Ended June 30, 2009
Per Share Operating Data
Net asset value, beginning of period	$	19.40	$	19.72	$	14.77	$	12.46	$	16.39
Income (loss) from investment operations:
Net investment loss2		(0.05)		(0.11)		(0.09)		(0.10)		(0.03)
Net realized and unrealized gain (loss)		3.98		(0.21)		5.04		2.41		(3.87)
Total from investment operations		3.93		(0.32)		4.95		2.31		(3.90)
Dividends and/or distributions to shareholders:
Dividends from net investment income		0.00		0.00		0.00		0.00		0.00
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.03)
Total dividends and/or distributions to shareholders		0.00		0.00		0.00		0.00		(0.03)
Net asset value, end of period	$	23.33	$	19.40	$	19.72	$	14.77	$	12.46
Total Return, at Net Asset Value3		20.26%		(1.62)%		33.51%		18.54%		(23.77)%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	57,999	$	69,088	$	102,861	$	106,797	$	132,615
Average net assets (in thousands)	$	62,574	$	76,237	$	107,948	$	129,492	$	160,939
Ratios to average net assets:4
Net investment loss		(0.22)%		(0.63)%		(0.51)%		(0.65)%		(0.21)%
Total expenses5		2.26%		2.33%		2.29%		2.35%		2.22%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		2.06%		2.06%		2.04%		2.05%		2.02%
Portfolio turnover rate		101 %		81 %		86 %		101 %		95 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective 2013 and 2012 fiscal years. See Note 1 of the accompanying Notes.

2. Per share amounts calculated based on the average shares outstanding during the period.

3. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

4. Annualized for periods less than one full year.

5. Total expenses including indirect expenses from affiliated fund were as follows:

Year Ended June 28, 2013	2.26	%
Year Ended June 29, 2012	2.33	%
Year Ended June 30, 2011	2.29	%
Year Ended June 30, 2010	2.35	%
Year Ended June 30, 2009	2.22	%

See accompanying Notes to Financial Statements.

20      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Class C	Year Ended June 28, 20131		Year Ended June 29, 20121		Year Ended June 30, 2011		Year Ended June 30, 2010		Year Ended June 30, 2009
Per Share Operating Data
Net asset value, beginning of period	$	19.53	$	19.84	$	14.85	$	12.53	$	16.47
Income (loss) from investment operations:
Net investment loss2		(0.03)		(0.10)		(0.08)		(0.09)		(0.02)
Net realized and unrealized gain (loss)		4.01		(0.21)		5.07		2.41		(3.89)
Total from investment operations		3.98		(0.31)		4.99		2.32		(3.91)
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.04)		0.00		0.00		0.00		0.00
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.03)
Total dividends and/or distributions to shareholders		(0.04)		0.00		0.00		0.00		(0.03)
Net asset value, end of period	$	23.47	$	19.53	$	19.84	$	14.85	$	12.53
Total Return, at Net Asset Value3		20.39%		(1.56)%		33.60%		18.52%		(23.72)%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	334,870	$	320,566	$	384,059	$	329,180	$	310,094
Average net assets (in thousands)	$	326,360	$	327,119	$	369,499	$	350,612	$	342,312
Ratios to average net assets:4
Net investment loss		(0.13)%		(0.56)%		(0.45)%		(0.63)%		(0.18)%
Total expenses5		1.94%		2.00%		1.99%		2.06%		2.08%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		1.94%		2.00%		1.97%		2.01%		1.98%
Portfolio turnover rate		101 %		81 %		86 %		101 %		95 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective 2013 and 2012 fiscal years. See Note 1 of the accompanying Notes.

2. Per share amounts calculated based on the average shares outstanding during the period.

3. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

4. Annualized for periods less than one full year.

5. Total expenses including indirect expenses from affiliated fund were as follows:

Year Ended June 28, 2013	1.94	%
Year Ended June 29, 2012	2.00	%
Year Ended June 30, 2011	1.99	%
Year Ended June 30, 2010	2.06	%
Year Ended June 30, 2009	2.08	%

See accompanying Notes to Financial Statements.

21      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

FINANCIAL HIGHLIGHTS    Continued

Class I	Period Ended June 28, 20131,2
Per Share Operating Data
Net asset value, beginning of period	$	23.31
Income (loss) from investment operations:
Net investment income3		0.20
Net realized and unrealized gain		4.33
Total from investment operations		4.53
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.32)
Distributions from net realized gain		0.00
Total dividends and/or distributions to shareholders		(0.32)
Net asset value, end of period	$	27.52
Total Return, at Net Asset Value4		19.65%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	362,310
Average net assets (in thousands)	$	68,428
Ratios to average net assets:5
Net investment income		1.08%
Total expenses6		0.66%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.66%
Portfolio turnover rate		101 %

1. June 28, 2013 represents the last business day of the Fund’s 2013 fiscal year. See Note 1 of the accompanying Notes.

2. For the period from October 26, 2012 (inception of offering) to June 28, 2013.

3. Per share amounts calculated based on the average shares outstanding during the period.

4. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

5. Annualized for periods less than one full year.

6. Total expenses including indirect expenses from affiliated fund were as follows:

Period Ended June 28, 2013 0.66 % 

See accompanying Notes to Financial Statements.

22      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Class N	Year Ended June 28, 20131		Year Ended June 29, 20121		Year Ended June 30, 2011		Year Ended June 30, 2010		Year Ended June 30, 2009
Per Share Operating Data
Net asset value, beginning of period	$	21.07	$	21.30	$	15.86	$	13.32	$	17.42
Income (loss) from investment operations:
Net investment income (loss)2		0.08		(0.01)		0.01		(0.02)		0.04
Net realized and unrealized gain (loss)		4.31		(0.22)		5.43		2.57		(4.11)
Total from investment operations		4.39		(0.23)		5.44		2.55		(4.07)
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.11)		0.00		0.00		(0.01)		0.00
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.03)
Total dividends and/or distributions to shareholders		(0.11)		0.00		0.00		(0.01)		(0.03)
Net asset value, end of period	$	25.35	$	21.07	$	21.30	$	15.86	$	13.32
Total Return, at Net Asset Value3		20.94%		(1.08)%		34.30%		19.15%		(23.34)%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	224,448	$	227,261	$	273,682	$	242,128	$	205,574
Average net assets (in thousands)	$	221,263	$	232,102	$	269,808	$	244,540	$	210,488
Ratios to average net assets:4
Net investment income (loss)		0.33%		(0.07)%		0.03%		(0.11)%		0.31%
Total expenses5		1.53%		1.57%		1.60%		1.68%		1.79%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		1.49%		1.51%		1.49%		1.49%		1.49%
Portfolio turnover rate		101 %		81 %		86 %		101 %		95 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective 2013 and 2012 fiscal years. See Note 1 of the accompanying Notes.

2. Per share amounts calculated based on the average shares outstanding during the period.

3. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

4. Annualized for periods less than one full year.

5. Total expenses including indirect expenses from affiliated fund were as follows:

Year Ended June 28, 2013	1.53	%
Year Ended June 29, 2012	1.57	%
Year Ended June 30, 2011	1.60	%
Year Ended June 30, 2010	1.68	%
Year Ended June 30, 2009	1.79	%

See accompanying Notes to Financial Statements.

23      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

FINANCIAL HIGHLIGHTS    Continued

Class Y	Year Ended June 28, 20131		Year Ended June 29, 20121		Year Ended June 30, 2011		Year Ended June 30, 2010		Year Ended June 30, 2009
Per Share Operating Data
Net asset value, beginning of period	$	22.88	$	23.12	$	17.17	$	14.38	$	18.75
Income (loss) from investment operations:
Net investment income2		0.25		0.13		0.14		0.10		0.13
Net realized and unrealized gain (loss)		4.68		(0.24)		5.89		2.77		(4.44)
Total from investment operations		4.93		(0.11)		6.03		2.87		(4.31)
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.28)		(0.13)		(0.08)		(0.08)		(0.03)
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.03)
Total dividends and/or distributions to shareholders		(0.28)		(0.13)		(0.08)		(0.08)		(0.06)
Net asset value, end of period	$	27.53	$	22.88	$	23.12	$	17.17	$	14.38
Total Return, at Net Asset Value3		21.74%		(0.40)%		35.14%		20.00%		(22.93)%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	789,137	$	908,339	$	1,059,058	$	828,624	$	877,926
Average net assets (in thousands)	$	977,581	$	904,802	$	992,951	$	914,353	$	926,200
Ratios to average net assets:4
Net investment income		1.00%		0.60%		0.69%		0.55%		0.93%
Total expenses5		0.81%		0.85%		0.83%		0.83%		0.89%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.81%		0.85%		0.83%		0.83%		0.89%
Portfolio turnover rate		101 %		81 %		86 %		101 %		95 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective 2013 and 2012 fiscal years. See Note 1 of the accompanying Notes.

2. Per share amounts calculated based on the average shares outstanding during the period.

3. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

4. Annualized for periods less than one full year.

5. Total expenses including indirect expenses from affiliated fund were as follows:

Year Ended June 28, 2013	0.81	%
Year Ended June 29, 2012	0.85	%
Year Ended June 30, 2011	0.83	%
Year Ended June 30, 2010	0.83	%
Year Ended June 30, 2009	0.89	%

See accompanying Notes to Financial Statements.

24      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

NOTES TO FINANCIAL STATEMENTS

1. Significant Accounting Policies

Oppenheimer Main Street Small-& Mid-Cap Fund (the “Fund”) is a diversified open-end management investment company registered under the Investment Company Act of 1940, as amended. The Fund’s investment objective is to seek capital appreciation. The Fund’s investment adviser was OppenheimerFunds, Inc. (“OFI” or the “Sub-Adviser”) through December 31, 2012. Effective January 1, 2013, the Fund’s investment adviser is OFI Global Asset Management, Inc. (“OFI Global” or the “Manager”), a wholly-owned subsidiary of OFI. The Manager has entered into a sub-advisory agreement with OFI, as of the same effective date.

The Fund offers Class A, Class C, Class I, Class N and Class Y shares, and previously offered Class B shares for new purchase through June 29, 2012. Subsequent to that date, no new purchases of Class B shares are permitted, however reinvestment of dividend and/or capital gain distributions and exchanges of Class B shares into and from other Oppenheimer funds will be allowed. Class A shares are sold at their offering price, which is normally net asset value plus a front-end sales charge. Class C and Class N shares are sold, and Class B shares were sold, without a front-end sales charge but may be subject to a contingent deferred sales charge (“CDSC”). Class N shares are sold only through retirement plans. Retirement plans that offer Class N shares may impose charges on those accounts. Class I and Class Y shares are sold to certain institutional investors or intermediaries without either a front-end sales charge or a CDSC, however, the intermediaries may impose charges on their accountholders who beneficially own Class I and Class Y shares. All classes of shares have identical rights and voting privileges with respect to the Fund in general and exclusive voting rights on matters that affect that class alone. Earnings, net assets and net asset value per share may differ due to each class having its own expenses, such as transfer and shareholder servicing agent fees and shareholder communications, directly attributable to that class. Class A, B, C and N shares have separate distribution and/or service plans under which they pay fees. Class I and Class Y shares do not pay such fees. Class B shares will automatically convert to Class A shares 72 months after the date of purchase.

The following is a summary of significant accounting policies consistently followed by the Fund.

Annual Periods. The Fund’s financial statements are presented through the last day the New York Stock Exchange was open for trading during each reporting period. The Fund’s financial statements have been presented through those dates to maintain consistency with the Fund’s net asset value calculations used for shareholder transactions.

Investment in Oppenheimer Institutional Money Market Fund. The Fund is permitted to invest daily available cash balances in an affiliated money market fund. The Fund may invest the available cash in Class E shares of Oppenheimer Institutional Money Market Fund (“IMMF”) to seek current income while preserving liquidity. IMMF is a registered open-end management investment company, regulated as a money market fund under the Investment Company Act of 1940, as amended. The Manager is the investment adviser of IMMF, and the Sub-Adviser provides investment and related advisory services to IMMF. When applicable, the Fund’s investment in IMMF is included in the Statement of Investments. Shares of IMMF are

25      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

NOTES TO FINANCIAL STATEMENTS     Continued

1. Significant Accounting Policies (Continued)

valued at their net asset value per share. As a shareholder, the Fund is subject to its proportional share of IMMF’s Class E expenses, including its management fee. The Manager will waive fees and/or reimburse Fund expenses in an amount equal to the indirect management fees incurred through the Fund’s investment in IMMF.

Allocation of Income, Expenses, Gains and Losses. Income, expenses (other than those attributable to a specific class), gains and losses are allocated on a daily basis to each class of shares based upon the relative proportion of net assets represented by such class. Operating expenses directly attributable to a specific class are charged against the operations of that class.

Federal Taxes. The Fund intends to comply with provisions of the Internal Revenue Code applicable to regulated investment companies and to distribute substantially all of its investment company taxable income, including any net realized gain on investments not offset by capital loss carryforwards, if any, to shareholders. Therefore, no federal income or excise tax provision is required. The Fund files income tax returns in U.S. federal and applicable state jurisdictions. The statute of limitations on the Fund’s tax return filings generally remain open for the three preceding fiscal reporting period ends.

The tax components of capital shown in the following table represent distribution requirements the Fund must satisfy under the income tax regulations, losses the Fund may be able to offset against income and gains realized in future years and unrealized appreciation or depreciation of securities and other investments for federal income tax purposes.

Undistributed Net Investment Income	Undistributed Long-Term Gain		Accumulated Loss Carryforward1,2,3		Net Unrealized Appreciation Based on Cost of Securities and Other Investments for Federal Income Tax Purposes
$564,633		$—		$262,026,549		$654,925,035

1. As of June 28, 2013, the Fund had $262,026,549 of net capital loss carryforwards available to offset future realized capital gains, if any, and thereby reduce future taxable gain distributions. Details of the capital loss carryforwards are included in the table below. Capital loss carryovers with no expiration, if any, must be utilized prior to those with expiration dates.

Expiring
2018	$	262,026,549

2. During the fiscal year ended June 28, 2013, the Fund utilized $428,694,170 of capital loss carryforward to offset capital gains realized in that fiscal year.

3. During the fiscal year ended June 29, 2012, the Fund utilized $242,307,123 of capital loss carryforward to offset capital gains realized in that fiscal year.

Net investment income (loss) and net realized gain (loss) may differ for financial statement and tax purposes. The character of dividends and distributions made during the fiscal year

26      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

1. Significant Accounting Policies (Continued)

from net investment income or net realized gains may differ from their ultimate characterization for federal income tax purposes. Also, due to timing of dividends and distributions, the fiscal year in which amounts are distributed may differ from the fiscal year in which the income or net realized gain was recorded by the Fund.

Accordingly, the following amounts have been reclassified for June 30, 2013. Net assets of the Fund were unaffected by the reclassifications.

Reduction to Paid-in Capital	Increase to Accumulated Net Investment Income		Increase to Accumulated Net Realized Loss on Investments
$653		$1,784,440		$1,783,787

The tax character of distributions paid during the years ended June 30, 2013 and June 30, 2012 was as follows:

	Year Ended  June 30, 2013		Year Ended  June 30, 2012
Distributions paid from:
Ordinary income	$	25,999,711	$	9,346,356

The aggregate cost of securities and other investments and the composition of unrealized appreciation and depreciation of securities and other investments for federal income tax purposes as of June 28, 2013 are noted in the following table. The primary difference between book and tax appreciation or depreciation of securities and other investments, if applicable, is attributable to the tax deferral of losses or tax realization of financial statement unrealized gain or loss.

Federal tax cost of securities	$	2,849,926,978
Gross unrealized appreciation	$	681,961,099
Gross unrealized depreciation		(27,036,064)
Net unrealized appreciation	$	654,925,035

Trustees’ Compensation. The Board of Trustees has adopted a compensation deferral plan for independent trustees that enables trustees to elect to defer receipt of all or a portion of the annual compensation they are entitled to receive from the Fund. For purposes of determining the amount owed to the Trustee under the plan, deferred amounts are treated as though equal dollar amounts had been invested in shares of the Fund or in other Oppenheimer funds selected by the Trustee. The Fund purchases shares of the funds selected for deferral by the Trustee in amounts equal to his or her deemed investment, resulting in a Fund asset equal to the deferred compensation liability. Such assets are included as a component of “Other” within the asset section of the Statement of Assets and Liabilities. Deferral of trustees’ fees under the plan will not affect the net assets of the Fund, and will not materially affect the Fund’s assets, liabilities or net investment income per share. Amounts will be deferred until distributed in accordance with the compensation deferral plan.

27          OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

NOTES TO FINANCIAL STATEMENTS    Continued

1. Significant Accounting Policies (Continued)

Dividends and Distributions to Shareholders. Dividends and distributions to shareholders, which are determined in accordance with income tax regulations and may differ from U.S. generally accepted accounting principles, are recorded on the ex-dividend date. Income and capital gain distributions, if any, are declared and paid annually or at other times as deemed necessary by the Manager.

Investment Income. Dividend income is recorded on the ex-dividend date or upon ex-dividend notification in the case of certain foreign dividends where the ex-dividend date may have passed. Non-cash dividends included in dividend income, if any, are recorded at the fair market value of the securities received. Interest income is recognized on an accrual basis. Discount and premium, which are included in interest income on the Statement of Operations, are amortized or accreted daily.

Custodian Fees. “Custodian fees and expenses” in the Statement of Operations may include interest expense incurred by the Fund on any cash overdrafts of its custodian account during the period. Such cash overdrafts may result from the effects of failed trades in portfolio securities and from cash outflows resulting from unanticipated shareholder redemption activity. The Fund pays interest to its custodian on such cash overdrafts, to the extent they are not offset by positive cash balances maintained by the Fund, at a rate equal to the Federal Funds Rate plus 0.50%. The “Reduction to custodian expenses” line item, if applicable, represents earnings on cash balances maintained by the Fund during the period. Such interest expense and other custodian fees may be paid with these earnings.

Security Transactions. Security transactions are recorded on the trade date. Realized gains and losses on securities sold are determined on the basis of identified cost.

Indemnifications. The Fund’s organizational documents provide current and former trustees and officers with a limited indemnification against liabilities arising in connection with the performance of their duties to the Fund. In the normal course of business, the Fund may also enter into contracts that provide general indemnifications. The Fund’s maximum exposure under these arrangements is unknown as this would be dependent on future claims that may be made against the Fund. The risk of material loss from such claims is considered remote.

Other. The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates.

28      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

2. Securities Valuation

The Fund calculates the net asset value of its shares as of the close of the New York Stock Exchange (the “Exchange”), normally 4:00 P.M. Eastern time, on each day the Exchange is open for trading.

The Fund’s Board has adopted procedures for the valuation of the Fund’s securities and has delegated the day-to-day responsibility for valuation determinations under those procedures to the Manager. The Manager has established a Valuation Committee which is responsible for determining a “fair valuation” for any security for which market quotations are not “readily available.” The Valuation Committee’s fair valuation determinations are subject to review, approval and ratification by the Fund’s Board at its next regularly scheduled meeting covering the calendar quarter in which the fair valuation was determined.

Valuation Methods and Inputs

Securities are valued using unadjusted quoted market prices, when available, as supplied primarily by third party pricing services or dealers.

The following methodologies are used to determine the market value or the fair value of the types of securities described below:

Securities traded on a registered U.S. securities exchange (including exchange-traded derivatives other than futures and futures options) are valued based on the last sale price of the security reported on the principal exchange on which it is traded, prior to the time when the Fund’s assets are valued. In the absence of a sale, the security is valued at the last sale price on the prior trading day, if it is within the spread of the current day’s closing “bid” and “asked” prices, and if not, at the current day’s closing bid price. A security of a foreign issuer traded on a foreign exchange but not listed on a registered U.S. securities exchange is valued based on the last sale price on the principal exchange on which the security is traded, as identified by the third party pricing service used by the Manager, prior to the time when the Fund’s assets are valued. If the last sale price is unavailable, the security is valued at the most recent official closing price on the principal exchange on which it is traded. If the last sales price or official closing price for a foreign security is not available, the security is valued at the mean between the bid and asked price per the exchange or, if not available from the exchange, obtained from two dealers. If bid and asked prices are not available from either the exchange or two dealers, the security is valued by using one of the following methodologies (listed in order of priority); (1) using a bid from the exchange, (2) the mean between the bid and asked price as provided by a single dealer, or (3) a bid from a single dealer.

Shares of a registered investment company that are not traded on an exchange are valued at that investment company’s net asset value per share.

Corporate and government debt securities (of U.S. or foreign issuers) and municipal debt securities, event-linked bonds, loans, mortgage-backed securities, collateralized mortgage obligations, and asset-backed securities are valued at the mean between the “bid” and “asked” prices utilizing evaluated prices obtained from third party pricing services or broker-dealers who may use matrix pricing methods to determine the evaluated prices.

Short-term money market type debt securities with a remaining maturity of sixty days or less are valued at cost adjusted by the amortization of discount or premium to maturity (amortized cost), which approximates market value. Short-term debt securities with a

29         OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

NOTES TO FINANCIAL STATEMENTS    Continued

2. Securities Valuation (Continued)

remaining maturity in excess of sixty days are valued at the mean between the “bid” and “asked” prices utilizing evaluated prices obtained from third party pricing services or broker-dealers.

A description of the standard inputs that may generally be considered by the third party pricing vendors in determining their evaluated prices is provided below.

Security Type	Standard inputs generally considered by third-party pricing vendors
Corporate debt, government debt, municipal, mortgage-backed and asset-backed securities	Reported trade data, broker-dealer price quotations, benchmark yields, issuer spreads on comparable securities, the credit quality, yield, maturity, and other appropriate factors.
Loans	Information obtained from market participants regarding reported trade data and broker-dealer price quotations.
Event-linked bonds	Information obtained from market participants regarding reported trade data and broker-dealer price quotations.

If a market value or price cannot be determined for a security using the methodologies described above, or if, in the “good faith” opinion of the Manager, the market value or price obtained does not constitute a “readily available market quotation,” or a significant event has occurred that would materially affect the value of the security the security is fair valued either (i) by a standardized fair valuation methodology applicable to the security type or the significant event as previously approved by the Valuation Committee and the Fund’s Board or (ii) as determined in good faith by the Manager’s Valuation Committee. The Valuation Committee considers all relevant facts that are reasonably available, through either public information or information available to the Manager, when determining the fair value of a security. Fair value determinations by the Manager are subject to review, approval and ratification by the Fund’s Board at its next regularly scheduled meeting covering the calendar quarter in which the fair valuation was determined. Those fair valuation standardized methodologies include, but are not limited to, valuing securities at the last sale price or initially at cost and subsequently adjusting the value based on: changes in company specific fundamentals, changes in an appropriate securities index, or changes in the value of similar securities which may be further adjusted for any discounts related to security-specific resale restrictions. When possible, such methodologies use observable market inputs such as unadjusted quoted prices of similar securities, observable interest rates, currency rates and yield curves. The methodologies used for valuing securities are not necessarily an indication of the risks associated with investing in those securities nor can it be assured that the Fund can obtain the fair value assigned to a security if it were to sell the security.

To assess the continuing appropriateness of security valuations, the Manager, or its third party service provider who is subject to oversight by the Manager, regularly compares prior day prices, prices on comparable securities, and sale prices to the current day prices and challenges those prices exceeding certain tolerance levels with the third party pricing service or broker source. For those securities valued by fair valuations, whether through a

30      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

2. Securities Valuation (Continued)

standardized fair valuation methodology or a fair valuation determination, the Valuation Committee reviews and affirms the reasonableness of the valuations based on such methodologies and fair valuation determinations on a regular basis after considering all relevant information that is reasonably available.

Classifications

Each investment asset or liability of the Fund is assigned a level at measurement date based on the significance and source of the inputs to its valuation. Various data inputs are used in determining the value of each of the Fund’s investments as of the reporting period end. These data inputs are categorized in the following hierarchy under applicable financial accounting standards:

1) Level 1-unadjusted quoted prices in active markets for identical assets or liabilities (including securities actively traded on a securities exchange)

2) Level 2-inputs other than unadjusted quoted prices that are observable for the asset or liability (such as unadjusted quoted prices for similar assets and market corroborated inputs such as interest rates, prepayment speeds, credit risks, etc.)

3) Level 3-significant unobservable inputs (including the Manager’s own judgments about assumptions that market participants would use in pricing the asset or liability).

The inputs used for valuing securities are not necessarily an indication of the risks associated with investing in those securities.

The table below categorizes amounts that are included in the Fund’s Statement of Assets and Liabilities as of June 28, 2013 based on valuation input level:

	Level 1— Unadjusted Quoted Prices		Level 2— Other Significant Observable Inputs		Level 3— Significant Unobservable Inputs		Value
Assets Table
Investments, at Value:
Common Stocks
Consumer Discretionary	$	560,629,719	$	—	$	—	$	560,629,719
Consumer Staples		101,732,936		—		—		101,732,936
Energy		305,903,806		—		—		305,903,806
Financials		864,572,615		—		—		864,572,615
Health Care		450,868,617		—		—		450,868,617
Industrials		626,046,393		—		—		626,046,393
Information Technology		364,723,334		—		—		364,723,334
Materials		143,045,489		—		—		143,045,489
Utilities		19,121,757		—		—		19,121,757
Investment Company		68,207,347		—		—		68,207,347
Total Assets	$	3,504,852,013	$	—	$	—	$	3,504,852,013

Currency contracts and forwards, if any, are reported at their unrealized appreciation/ depreciation at measurement date, which represents the change in the contract’s value from trade date. Futures, if any, are reported at their variation margin at measurement date, which

31      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

NOTES TO FINANCIAL STATEMENTS    Continued

2. Securities Valuation (Continued)

represents the amount due to/from the Fund at that date. All additional assets and liabilities included in the above table are reported at their market value at measurement date.

3. Shares of Beneficial Interest

The Fund has authorized an unlimited number of $0.001 par value shares of beneficial interest of each class. Transactions in shares of beneficial interest were as follows:

	Year Ended June 28, 2013				Year Ended June 29, 2012
	Shares		Amount		Shares		Amount
Class A
Sold		10,588,591	$	252,903,739		10,534,968	$	217,777,232
Dividends and/or distributions reinvested		555,919		12,580,458		192,909		3,653,701
Redeemed		(21,983,108)		(528,428,274)		(26,485,815)		(538,082,542)
Net decrease		(10,838,598)	$	(262,944,077)		(15,757,938)	$	(316,651,609)
Class B
Sold		126,495	$	2,732,190		492,331	$	9,100,716
Dividends and/or distributions reinvested		—		—		—		—
Redeemed		(1,201,449)		(25,265,399)		(2,147,309)		(40,328,611)
Net decrease		(1,074,954)	$	(22,533,209)		(1,654,978)	$	(31,227,895)
Class C
Sold		1,632,468	$	35,151,487		1,802,033	$	33,537,173
Dividends and/or distributions reinvested		24,649		502,362		—		—
Redeemed		(3,801,975)		(81,124,131)		(4,745,752)		(87,251,919)
Net decrease		(2,144,858)	$	(45,470,282)		(2,943,719)	$	(53,714,746)
Class I
Sold		13,356,323	$	369,277,881		—	$	—
Dividends and/or distributions reinvested		—		—		—		—
Redeemed		(189,209)		(5,211,387)		—		—
Net increase		13,167,114	$	364,066,494		—	$	—
Class N
Sold		2,228,614	$	51,131,899		2,700,750	$	53,824,937
Dividends and/or distributions reinvested		46,182		1,013,700		—		—
Redeemed		(4,206,086)		(95,450,389)		(4,764,737)		(94,149,120)
Net decrease		(1,931,290)	$	(43,304,790)		(2,063,987)	$	(40,324,183)

32      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

3. Shares of Beneficial Interest (Continued)

	Year Ended June 28, 2013				Year Ended June 29, 2012
	Shares		Amount		Shares		Amount
Class Y
Sold		11,105,008	$	276,779,104		8,968,365	$	190,190,757
Dividends and/or distributions reinvested		440,420		10,464,383		257,688		5,122,831
Redeemed		(22,586,032)		(599,816,639)		(15,323,841)		(327,039,609)
Net decrease		(11,040,604)	$	(312,573,152)		(6,097,788)	$	(131,726,021)

4. Purchases and Sales of Securities

The aggregate cost of purchases and proceeds from sales of securities, other than short-term obligations and investments in IMMF, for the year ended June 28, 2013 were as follows:

	Purchases		Sales
Investment securities		$3,265,176,127		$3,550,716,651

5. Fees and Other Transactions with Affiliates

Management Fees. Under the investment advisory agreement, the Fund pays the Manager a management fee based on the daily net assets of the Fund at an annual rate as shown in the following table:

Fee Schedule
Up to $200 million	0.75%
Next $200 million	0.72
Next $200 million	0.69
Next $200 million	0.66
Next $4.2 billion	0.60
Over $5.0 billion	0.58

Sub-Adviser Fees. The Manager has retained the Sub-Adviser to provide the day-to-day portfolio management of the Fund. Under the Sub-Advisory Agreement, the Manager pays the Sub-Adviser an annual fee in monthly installments, equal to a percentage of the investment management fee collected by the Manager from the Fund, which shall be calculated after any investment management fee waivers. The fee paid to the Sub-Adviser is paid by the Manager, not by the Fund.

Transfer Agent Fees. OppenheimerFunds Services (“OFS”), a division of OFI, acted as the transfer and shareholder servicing agent for the Fund through December 31, 2012. Effective January 1, 2013, OFI Global (the “Transfer Agent”) serves as the transfer and shareholder servicing agent for the Fund. Fees incurred by the Fund with respect to these services are detailed in the Statement of Operations.

33      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

NOTES TO FINANCIAL STATEMENTS    Continued

5. Fees and Other Transactions with Affiliates (Continued)

Sub-Transfer Agent Fees. Effective January 1, 2013, the Transfer Agent has retained Shareholder Services, Inc., a wholly-owned subsidiary of OFI (the “Sub-Transfer Agent”), to provide the day-to-day transfer agent and shareholder servicing of the Fund. Under the Sub-Transfer Agency Agreement, the Transfer Agent pays the Sub-Transfer Agent an annual fee in monthly installments, equal to a percentage of the transfer agent fee collected by the Transfer Agent from the Fund, which shall be calculated after any applicable fee waivers. The fee paid to the Sub-Transfer Agent is paid by the Transfer Agent, not by the Fund.

Distribution and Service Plan (12b-1) Fees. Under its General Distributor’s Agreement with the Fund, OppenheimerFunds Distributor, Inc. (the “Distributor”) acts as the Fund’s principal underwriter in the continuous public offering of the Fund’s classes of shares.

Service Plan for Class A Shares. The Fund has adopted a Service Plan (the “Plan”) for Class A shares under Rule 12b-1 of the Investment Company Act of 1940. Under the Plan, the Fund reimburses the Distributor for a portion of its costs incurred for services provided to accounts that hold Class A shares. Reimbursement is made periodically at an annual rate of up to 0.25% of the daily net assets of Class A shares of the Fund. The Distributor currently uses all of those fees to pay dealers, brokers, banks and other financial institutions periodically for providing personal service and maintenance of accounts of their customers that hold Class A shares. Any unreimbursed expenses the Distributor incurs with respect to Class A shares in any fiscal year cannot be recovered in subsequent periods. Fees incurred by the Fund under the Plan are detailed in the Statement of Operations.

Distribution and Service Plans for Class B, Class C and Class N Shares. The Fund has adopted Distribution and Service Plans (the “Plans”) for Class B, Class C and Class N shares under Rule 12b-1 of the Investment Company Act of 1940 to compensate the Distributor for its services in connection with the distribution of those shares and servicing accounts. Under the Plans, the Fund pays the Distributor an annual asset-based sales charge of 0.75% on Class B and Class C shares daily net assets and 0.25% on Class N shares daily net assets. The Distributor also receives a service fee of 0.25% per year under each plan. If either the Class B, Class C or Class N plan is terminated by the Fund or by the shareholders of a class, the Board of Trustees and its independent trustees must determine whether the Distributor shall be entitled to payment from the Fund of all or a portion of the service fee and/or asset-based sales charge in respect to shares sold prior to the effective date of such termination. Fees incurred by the Fund under the Plans are detailed in the Statement of Operations. The Distributor determines its uncompensated expenses under the Plans at calendar quarter ends. The Distributor’s aggregate uncompensated expenses under the Plans at June 30, 2013 were as follows:

Class C	$	12,108,411
Class N		7,090,925

Sales Charges. Front-end sales charges and contingent deferred sales charges (“CDSC”) do not represent expenses of the Fund. They are deducted from the proceeds of sales of Fund

34      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

5. Fees and Other Transactions with Affiliates (Continued)

shares prior to investment or from redemption proceeds prior to remittance, as applicable. The sales charges retained by the Distributor from the sale of shares and the CDSC retained by the Distributor on the redemption of shares is shown in the following table for the period indicated.

Year Ended	Class A Front-End Sales Charges Retained by Distributor		Class A Contingent Deferred Sales Charges Retained by Distributor		Class B Contingent Deferred Sales Charges Retained by Distributor		Class C Contingent Deferred Sales Charges Retained by Distributor		Class N   Contingent   Deferred   Sales   Charges   Retained by   Distributor
June 28, 2013		$296,144		$832		$94,380		$9,367		$999

Waivers and Reimbursements of Expenses. The Manager will waive fees and/or reimburse Fund expenses in an amount equal to the indirect management fees incurred through the Fund’s investment in IMMF. During the year ended June 28, 2013, the Manager waived fees and/or reimbursed the Fund $96,415 for IMMF management fees.

The Transfer Agent has voluntarily agreed to limit transfer and shareholder servicing agent fees for Classes B, C, N and Y shares to 0.35% of average annual net assets per class and for Class A shares to 0.30% of average annual net assets of the class.

During the year ended June 28, 2013, the Transfer Agent waived transfer and shareholder servicing agent fees as follows:

Class B	$124,293
Class N	93,401

Some of these undertakings may be modified or terminated at any time; some may not be modified or terminated until after one year from the date of the current prospectus, as indicated therein.

6. Pending Litigation

Since 2009, a number of class action lawsuits have been pending in federal courts against OppenheimerFunds, Inc. (“OFI”), OppenheimerFunds Distributor, Inc., the Fund’s principal underwriter and distributor (the “Distributor”), and certain funds (but not including the Fund) advised by the Manager and distributed by the Distributor (the “Defendant Funds”). Several of these lawsuits also name as defendants certain officers and current and former trustees of the respective Defendant Funds. The lawsuits raise claims under federal securities law and allege, among other things, that the disclosure documents of the respective Defendant Funds contained misrepresentations and omissions and that the respective Defendant Funds’ investment policies were not followed. The plaintiffs in these actions seek unspecified damages, equitable relief and awards of attorneys’ fees and litigation expenses. The Defendant Funds’ Boards of Trustees have also engaged counsel to represent the Funds and the present and former Independent Trustees named in those suits.

35      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

NOTES TO FINANCIAL STATEMENTS    Continued

6. Pending Litigation (Continued)

Other class action and individual lawsuits have been filed since 2008 in various state and federal courts against OFI and certain of its affiliates by investors seeking to recover investments they allegedly lost as a result of the “Ponzi” scheme run by Bernard L. Madoff and his firm, Bernard L. Madoff Investment Securities, LLC (“BLMIS”). Plaintiffs in these suits allege that they suffered losses as a result of their investments in several funds managed by an affiliate of OFI and assert a variety of claims, including breach of fiduciary duty, fraud, negligent misrepresentation, unjust enrichment, and violation of federal and state securities laws and regulations, among others. They seek unspecified damages, equitable relief and awards of attorneys’ fees and litigation expenses. Neither the Distributor, nor any of the Oppenheimer mutual funds, their independent trustees or directors are named as defendants in these lawsuits. None of the Oppenheimer mutual funds invested in any funds or accounts managed by Madoff or BLMIS. On February 28, 2011, a stipulation of partial settlement of three groups of consolidated putative class action lawsuits relating to these matters was filed in the U.S. District Court for the Southern District of New York. On August 19, 2011, the court entered an order and final judgment approving the settlement as fair, reasonable and adequate. In September 2011, certain parties filed notices of appeal from the court’s order approving the settlement. The settlement does not resolve other outstanding lawsuits against OFI and its affiliates relating to BLMIS.

On April 16, 2010, a lawsuit was filed in New York state court against (i) OFI, (ii) an affiliate of OFI and (iii) AAArdvark IV Funding Limited (“AAArdvark IV”), an entity advised by OFI’s affiliate, in connection with investments made by the plaintiffs in AAArdvark IV. Plaintiffs allege breach of contract and common law fraud claims against the defendants and seek compensatory damages, costs and disbursements, including attorney fees. On April 11, 2013, the court granted defendants’ motion for summary judgment, dismissing plaintiffs’ fraud claim with prejudice and dismissing their contract claim without prejudice, and granted plaintiffs leave to replead their contract claim to assert a cause of action for specific performance within 30 days. On May 9, 2013, plaintiffs filed a notice of appeal from the court’s dismissal order. On July 15, 2011, a lawsuit was filed in New York state court against OFI, an affiliate of OFI and AAArdvark Funding Limited (“AAArdvark I”), an entity advised by OFI’s affiliate, in connection with investments made by the plaintiffs in AAArdvark I. The complaint alleges breach of contract and common law fraud claims against the defendants and seeks compensatory damages, costs and disbursements, including attorney fees. On November 9, 2011, a lawsuit was filed in New York state court against OFI, an affiliate of OFI and AAArdvark XS Funding Limited (“AAArdvark XS”), an entity advised by OFI’s affiliate, in connection with investments made by the plaintiffs in AAArdvark XS. The complaint alleges breach of contract against the defendants and seeks compensatory damages, costs and disbursements, including attorney fees.

OFI believes the lawsuits and appeals described above are without legal merit and, with the exception of actions it has settled, is defending against them vigorously. While it is premature to render any opinion as to the outcome in these lawsuits, or whether any costs that the Defendant Funds may bear in defending the suits might not be reimbursed by insurance, OFI believes that these suits should not impair the ability of OFI or the Distributor

36      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

6. Pending Litigation (Continued)

to perform their respective duties to the Fund, and that the outcome of all of the suits together should not have any material effect on the operations of any of the Oppenheimer mutual funds.

37      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

REPORT OF INDEPENDENT REGISTERED PUBLIC

ACCOUNTING FIRM

The Board of Trustees and Shareholders of Oppenheimer Main Street Small- & Mid-Cap Fund:

We have audited the accompanying statement of assets and liabilities of Oppenheimer Main Street Small- & Mid-Cap Fund, including the statement of investments, as of June 28, 2013, and the related statement of operations for the year then ended, the statements of changes in net assets for each of the years in the two-year period then ended, and the financial highlights for each of the years or periods in the five-year period then ended. These financial statements and financial highlights are the responsibility of the Fund’s management. Our responsibility is to express an opinion on these financial statements and financial highlights based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements and financial highlights are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. Our procedures included confirmation of securities owned as of June 28, 2013, by correspondence with the custodian and brokers, or by other appropriate auditing procedures where replies from brokers were not received. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements and financial highlights referred to above present fairly, in all material respects, the financial position of Oppenheimer Main Street Small- & Mid-Cap Fund as of June 28, 2013, the results of its operations for the year then ended, the changes in its net assets for each of the years in the two-year period then ended, and the financial highlights for each of the years or periods in the five-year period then ended, in conformity with U.S. generally accepted accounting principles.

KPMG LLP

Denver, Colorado

August 16, 2013

38      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

FEDERAL INCOME TAX INFORMATION      Unaudited

In early 2013, if applicable, shareholders of record received information regarding all dividends and distributions paid to them by the Fund during calendar year 2012.

Dividends, if any, paid by the Fund during the fiscal year ended June 28, 2013 which are not designated as capital gain distributions should be multiplied by the maximum amount allowable but not less than 65.48% to arrive at the amount eligible for the corporate dividend-received deduction.

A portion, if any, of the dividends paid by the Fund during the fiscal year ended June 28, 2013 which are not designated as capital gain distributions are eligible for lower individual income tax rates to the extent that the Fund has received qualified dividend income as stipulated by recent tax legislation. The maximum amount allowable but not less than $40,103,258 of the Fund’s fiscal year taxable income may be eligible for the lower individual income tax rates. In early 2013, shareholders of record received information regarding the percentage of distributions that are eligible for lower individual income tax rates.

Recent tax legislation allows a regulated investment company to designate distributions not designated as capital gain distributions, as either interest related dividends or short-term capital gain dividends, both of which are exempt from the U.S. withholding tax applicable to non U.S. taxpayers. For the fiscal year ended June 28, 2013, the maximum amount allowable but not less than $50,937 of the ordinary distributions to be paid by the Fund qualifies as an interest related dividend.

The foregoing information is presented to assist shareholders in reporting distributions received from the Fund to the Internal Revenue Service. Because of the complexity of the federal regulations which may affect your individual tax return and the many variations in state and local tax regulations, we recommend that you consult your tax advisor for specific guidance.

39      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

PORTFOLIO PROXY VOTING POLICIES AND PROCEDURES;

UPDATES TO STATEMENTS OF INVESTMENTS   Unaudited

The Fund has adopted Portfolio Proxy Voting Policies and Procedures under which the Fund votes proxies relating to securities (“portfolio proxies”) held by the Fund. A description of the Fund’s Portfolio Proxy Voting Policies and Procedures is available (i) without charge, upon request, by calling the Fund toll-free at 1.800.CALL OPP (225.5677), (ii) on the Fund’s website at oppenheimerfunds.com, and (iii) on the SEC’s website at www.sec.gov. In addition, the Fund is required to file Form N-PX, with its complete proxy voting record for the 12 months ended June 30th, no later than August 31st of each year. The Fund’s voting record is available (i) without charge, upon request, by calling the Fund toll-free at 1.800.CALL OPP (225.5677), and (ii) in the Form N-PX filing on the SEC’s website at www.sec.gov.

The Fund files its complete schedule of portfolio holdings with the SEC for the first quarter and the third quarter of each fiscal year on Form N-Q. The Fund’s Form N-Q filings are available on the SEC’s website at www.sec.gov. Those forms may be reviewed and copied at the SEC’s Public Reference Room in Washington, D.C. Information on the operation of the Public Reference Room may be obtained by calling 1-800-SEC-0330.

Householding—Delivery of Shareholder Documents

This is to inform you about OppenheimerFunds’ “householding” policy. If more than one member of your household maintains an account in a particular fund, OppenheimerFunds will mail only one copy of the fund’s prospectus (or, if available, the fund’s summary prospectus), annual and semiannual report and privacy policy. The consolidation of these mailings, called householding, benefits your fund through reduced mailing expense, and benefits you by reducing the volume of mail you receive from OppenheimerFunds. Householding does not affect the delivery of your account statements.

Please note that we will continue to household these mailings for as long as you remain an OppenheimerFunds shareholder, unless you request otherwise. If you prefer to receive multiple copies of these materials, please call us at 1.800.CALL-OPP (225-5677). You may also notify us in writing or via email. We will begin sending you individual copies of the prospectus (or, if available, the summary prospectus), reports and privacy policy within 30 days of receiving your request to stop householding.

40      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

TRUSTEES AND OFFICERS      Unaudited

Name, Position(s) Held with the Fund, Length of Service, Age	Principal Occupation(s) During the Past 5 Years; Other Trusteeships/Directorships Held; Number of Portfolios in the Fund Complex Currently Overseen
INDEPENDENT TRUSTEES	The address of each Trustee in the chart below is 6803 S. Tucson Way, Centennial, Colorado 80112-3924. Each Trustee serves for an indefinite term, or until his or her resignation, retirement, death or removal.
Sam Freedman, Chairman of the Board of Trustees (since 2012) and Trustee (since 1999) Year of Birth: 1940	Director of Colorado UpLIFT (charitable organization) (since September 1984). Mr. Freedman held several positions with the Sub-Adviser and with subsidiary or affiliated companies of the Sub-Adviser (until October 1994). Oversees 36 portfolios in the OppenheimerFunds complex. Mr. Freedman has served on the Boards of certain Oppenheimer funds since 1996, during which time he has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
Edward L. Cameron, Trustee (since 1999) Year of Birth: 1938	Member of The Life Guard of Mount Vernon (George Washington historical site) (June 2000-June 2006); Partner of PricewaterhouseCoopers LLP (accounting firm) (July 1974-June 1999); Chairman of Price Waterhouse LLP Global Investment Management Industry Services Group (accounting firm) (July 1994-June 1998). Oversees 36 portfolios in the OppenheimerFunds complex. Mr. Cameron has served on the Boards of certain Oppenheimer funds since 1999, during which time he has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
Jon S. Fossel, Trustee (since 1999) Year of Birth: 1942	Chairman of the Board (2006-December 2011) and Director (June 2002-December 2011) of UNUMProvident (insurance company); Director of Northwestern Energy Corp. (public utility corporation) (November 2004-December 2009); Director of P.R. Pharmaceuticals (October 1999-October 2003); Director of Rocky Mountain Elk Foundation (non-profit organization) (February 1998-February 2003 and February 2005-February 2007); Chairman and Director (until October 1996) and President and Chief Executive Officer (until October 1995) of the Sub-Adviser; President, Chief Executive Officer and Director of the following: Oppenheimer Acquisition Corp. (“OAC”) (parent holding company of the Sub-Adviser), Shareholders Services, Inc. and Shareholder Financial Services, Inc. (until October 1995). Oversees 36 portfolios in the OppenheimerFunds complex. Mr. Fossel has served on the Boards of certain Oppenheimer funds since 1990, during which time he has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
Richard F. Grabish, Trustee (since 2012) Year of Birth: 1948	Formerly Senior Vice President and Assistant Director of Sales and Marketing (March 1997-December 2007), Director (March 1987-December 2007) and Manager of Private Client Services (June 1985-June 2005) of A.G. Edwards & Sons, Inc. (broker/dealer and investment firm); Chairman and Chief Executive Officer of A.G. Edwards Trust Company, FSB (March 2001-December 2007); President and Vice Chairman of A.G. Edwards Trust Company, FSB (investment adviser) (April 1987-March 2001); President of A.G. Edwards Trust Company, FSB (investment adviser) (June 2005-December 2007). Oversees 36 portfolios in the OppenheimerFunds complex. Mr. Grabish has served on the Boards of certain Oppenheimer funds since 2001, during which time he has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.

41      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

TRUSTEES AND OFFICERS      Unaudited / Continued

Beverly L. Hamilton, Trustee (since 2002) Year of Birth: 1946	Trustee of Monterey Institute for International Studies (educational organization) (since February 2000); Board Member of Middlebury College (educational organization) (December 2005-June 2011); Chairman (since 2010) of American Funds’ Emerging Markets Growth Fund, Inc. (mutual fund); Director of The California Endowment (philanthropic organization) (April 2002-April 2008); Director (February 2002-2005) and Chairman of Trustees (2006-2007) of the Community Hospital of Monterey Peninsula; Director (October 1991-2005); Vice Chairman (2006-2009) of American Funds’ Emerging Markets Growth Fund, Inc. (mutual fund); President of ARCO Investment Management Company (February 1991-April 2000); Member of the investment committees of The Rockefeller Foundation (2001-2006) and The University of Michigan (since 2000); Advisor at Credit Suisse First Boston’s Sprout venture capital unit (venture capital fund) (1994-January 2005); Trustee of MassMutual Institutional Funds (investment company) (1996-June 2004); Trustee of MML Series Investment Fund (investment company) (April 1989-June 2004); Member of the investment committee of Hartford Hospital (2000-2003); and Advisor to Unilever (Holland) pension fund (2000-2003). Oversees 36 portfolios in the OppenheimerFunds complex. Ms. Hamilton has served on the Boards of certain Oppenheimer funds since 2002, during which time she has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
Victoria J. Herget, Trustee (since 2012) Year of Birth:1951	Independent Director of the First American Funds (mutual fund family) (2003-2011); former Managing Director (1993-2001), Principal (1985-1993), Vice President (1978-1985) and Assistant Vice President (1973-1978) of Zurich Scudder Investments (and its predecessor firms); Board Chair (2008-Present) and Director (2004-Present), United Educators (insurance company); Trustee (1992-2007), Chair of the Board of Trustees (1999-2007), Investment Committee Chair (1994-1999) and Investment Committee member (2007-2010) of Wellesley College; Trustee (since 2000) and Chair (since 2010), Newberry Library; Trustee, Mather LifeWays (since 2001); Trustee, BoardSource (2006-2009) and Chicago City Day School (1994-2005). Oversees 36 portfolios in the OppenheimerFunds complex. Ms. Herget has served on the Boards of certain Oppenheimer funds since 2012, during which time she has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
Robert J. Malone, Trustee (since 2002) Year of Birth: 1944	Chairman of the Board (since 2012) and Director (since August 2005) of Jones International University (educational organization) (since August 2005); Chairman, Chief Executive Officer and Director of Steele Street Bank Trust (commercial banking) (since August 2003); Trustee of the Gallagher Family Foundation (non-profit organization) (since 2000); Board of Directors of Opera Colorado Foundation (non-profit organization) (2008-2012); Director of Colorado UpLIFT (charitable organization) (1986-2010); Director of Jones Knowledge, Inc. (2006-2010); Former Chairman of U.S. Bank-Colorado (subsidiary of U.S. Bancorp and formerly Colorado National Bank) (July 1996-April 1999); Director of Commercial Assets, Inc. (real estate investment trust) (1993-2000); Director of U.S. Exploration, Inc. (oil and gas exploration) (1997-February 2004); Chairman of the Board (1991-1994) and Trustee (1985-1994) of Regis University; and Chairman of the Board (1990-1991 and Trustee (1984-1999) of Young Presidents Organization. Oversees 36 portfolios in the OppenheimerFunds complex. Mr. Malone has served on the Boards of certain Oppenheimer funds since 2002, during which time he has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.

42      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

F. William Marshall, Jr., Trustee (since 2000) Year of Birth: 1942	Trustee Emeritus of Worcester Polytech Institute (WPI) (private university) (since 2009); Trustee of MassMutual Select Funds (formerly MassMutual Institutional Funds) (investment company) (since 1996), MML Series Investment Fund (investment company) (since 1996) and Mass Mutual Premier Funds (investment company) (since January 2012); President and Treasurer of the SIS Fund (private charitable fund) (January 1999 – March 2011); Former Trustee of WPI (1985-2008); Former Chairman of the Board (2004-2006) and Former Chairman of the Investment Committee of WPI (1994-2008); Chairman of SIS & Family Bank, F.S.B. (formerly SIS Bank) (commercial bank) (January 1999-July 1999); Executive Vice President of Peoples Heritage Financial Group, Inc. (commercial bank) (January 1999-July 1999); and Former President and Chief Executive Officer of SIS Bancorp. (1993-1999). Oversees 40 portfolios in the OppenheimerFunds complex. Mr. Marshall has served on the Boards of certain Oppenheimer funds since 2000, during which time he has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
Karen L. Stuckey, Trustee (since 2012) Year of Birth: 1953	Partner (1990-2012) of PricewaterhouseCoopers LLP (held various positions 1975-1990); Emeritus Trustee (since 2006) and Trustee (1992-2006) and member of Executive, Nominating and Audit Committees and Chair of Finance Committee of Lehigh University; and member, Women’s Investment Management Forum since inception. Oversees 36 portfolios in the OppenheimerFunds complex. Ms. Stuckey has served on the Boards of certain Oppenheimer funds since 2012, during which time she has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
James D. Vaughn, Trustee (since 2012) Year of Birth:1945	Retired; former managing partner (1994-2001) of Denver office of Deloitte & Touche LLP, (held various positions 1969-1993); Trustee and Chairman of the Audit Committee of Schroder Funds (2003-2012); Board member and Chairman of Audit Committee of AMG National Trust Bank (since 2005); Trustee and Investment Committee member, University of South Dakota Foundation (since 1996); Board member, Audit Committee Member and past Board Chair, Junior Achievement (since 1993); former Board member, Mile High United Way, Boys and Girls Clubs, Boy Scouts, Colorado Business Committee for the Arts, Economic Club of Colorado and Metro Denver Network. Oversees 36 portfolios in the OppenheimerFunds complex. Mr. Vaughn has served on the Boards of certain Oppenheimer funds since 2012, during which time he has become familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.
INTERESTED TRUSTEE AND OFFICER	Mr. Glavin is an “Interested Trustee” because he is affiliated with the Manager and the Sub-Adviser by virtue of his positions as an officer and director of the Manager and a director of the Sub-Adviser, and as a shareholder of the Sub-Adviser’s parent company. Both as a Trustee and as an officer, he serves for an indefinite term, or until his resignation, retirement, death or removal. Mr. Glavin’s address is Two World Financial Center, 225 Liberty Street, 11th Floor, New York, New York 10281-1008.
William F. Glavin, Jr., Trustee, President and Principal Executive Officer (since 2009) Year of Birth: 1958	Director, Chairman and Chief Executive Officer of the Manager (since January 2013); President of the Manager (January 2013-May 2013); Chairman of the Sub-Adviser (December 2009-December 2012); Chief Executive Officer (January 2009-December 2012) and Director of the Sub-Adviser (since January 2009); President of the Sub-Adviser (May 2009-December 2012); Management Director (since June 2009), President (since December 2009) and Chief Executive Officer (since January 2011) of Oppenheimer Acquisition Corp. (“OAC”) (the Sub-Adviser’s parent holding company); Director of Oppenheimer Real Asset Management, Inc. (since March

43         OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

TRUSTEES AND OFFICERS      Unaudited / Continued

William F. Glavin, Jr. Continued	2010); Executive Vice President (March 2006-February 2009) and Chief Operating Officer (July 2007-February 2009) of Massachusetts Mutual Life Insurance Company (OAC’s parent company); Director (May 2004-March 2006) and Chief Operating Officer and Chief Compliance Officer (May 2004-January 2005), President (January 2005-March 2006) and Chief Executive Officer (June 2005-March 2006) of Babson Capital Management LLC; Director (March 2005-March 2006), President (May 2003-March 2006) and Chief Compliance Officer (July 2005-March 2006) of Babson Capital Securities, Inc. (a broker-dealer); President (May 2003-March 2006) of Babson Investment Company, Inc.; Director (May 2004-August 2006) of Babson Capital Europe Limited; Director (May 2004-October 2006) of Babson Capital Guernsey Limited; Director (May 2004-March 2006) of Babson Capital Management LLC; Non-Executive Director (March 2005-March 2007) of Baring Asset Management Limited; Director (February 2005-June 2006) Baring Pension Trustees Limited; Director and Treasurer (December 2003-November 2006) of Charter Oak Capital Management, Inc.; Director (May 2006-September 2006) of C.M. Benefit Insurance Company; Director (May 2008-June 2009) and Executive Vice President (June 2007-July 2009) of C.M. Life Insurance Company; President (March 2006-May 2007) of MassMutual Assignment Company; Director (January 2005-December 2006), Deputy Chairman (March 2005-December 2006) and President (February 2005-March 2005) of MassMutual Holdings (Bermuda) Limited; Director (May 2008-June 2009) and Executive Vice President (June 2007-July 2009) of MML Bay State Life Insurance Company; Chief Executive Officer and President (April 2007-January 2009) of MML Distributors, LLC; and Chairman (March 2006-December 2008) and Chief Executive Officer (May 2007-December 2008) of MML Investors Services, Inc. An officer of 86 portfolios in the OppenheimerFunds complex.
OTHER OFFICERS OF THE FUND	The addresses of the Officers in the chart below are as follows: for Messrs. Anello, Ziehl, Vardharaj, Krantz, Weiner, Gabinet and Mss. Budzinski, Ketner Pak and Nasta, Two World Financial Center, 225 Liberty Street, New York, New York 10281-1008, for Messrs. Vandehey and Wixted, 6803 S. Tucson Way, Centennial, Colorado 80112-3924. Each Officer serves for an indefinite term or until his or her resignation, retirement, death or removal.
Raymond Anello, Vice President (since 2011) Year of Birth: 1964	Vice President of the Sub-Adviser (since May 2009) and a portfolio manager of the Sub-Adviser (since April 2011). Sector manager for energy and utilities for the Sub-Adviser’s Main Street Investment Team (since May 2009). Portfolio Manager of the RS All Cap Dividend product (from its inception in July 2007-April 2009) and served as a sector manager for energy and utilities for various other RS Investments products. Guardian Life Insurance Company (October 1999) and transitioned to RS Investments (October 2006) in connection with Guardian Life Insurance Company’s acquisition of an interest in RS Investments. Mr. Anello served as an equity portfolio manager/analyst and high yield analyst at Orion Capital (1995-1998) and an assistant portfolio manager at the Garrison Bradford portfolio management firm (1988-1995). Mr. Anello is a portfolio manager and officer of other portfolios in the OppenheimerFunds complex.
Matthew P. Ziehl, Vice President (since 2009) Year of Birth: 1967	Vice President and Senior Portfolio Manager of the Sub-Adviser (since May 2009). Portfolio manager with RS Investment Management Co. LLC (October 2006-May 2009); Managing Director at The Guardian Life Insurance Company (December 2001-October 2006) when Guardian Life Insurance acquired an interest in RS Investment Management Co. LLC. Team leader and co portfolio manager with Salomon Brothers Asset Management, Inc. for small growth portfolios (January 2001-December 2001). A portfolio manager and officer of other portfolios in the OppenheimerFunds complex.

44      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Raman Vardharaj, Vice President (since 2009) Year of Birth: 1971	Vice President and portfolio manager of the Sub-Adviser (since May 2009). Sector manager and a senior quantitative analyst creating stock selection models, monitoring portfolio risks and analyzing portfolio performance across the RS Core Equity Team of RS Investment Management Co. LLC (October 2006-May 2009). Quantitative analyst at The Guardian Life Insurance Company of America (1998-October 2006) when Guardian Life Insurance acquired an interest in RS Investment Management Co. LLC. A portfolio manager and officer of other portfolios in the OppenheimerFunds complex.
Joy Budzinski, Vice President (since 2012) Year of Birth: 1968	Vice President of the Sub-Adviser (since May 2009) and a portfolio manager of the Sub-Adviser (since November 2012). Sector manager for healthcare for the Sub-Adviser’s Main Street Investment Team (since May 2009). Healthcare sector manager at RS Investment and Guardian Life Insurance Company. Guardian Life Insurance Company (August 2006) and transitioned to RS Investments (October 2006) in connection with Guardian Life Insurance Company’s acquisition of an interest in RS Investments. Senior equity analyst at Bank of New York BNY Asset Management (2001 -2006); portfolio manager and analyst at Alliance of America (1999-2001); portfolio manager and analyst at JP Morgan Chase (1993-1997); analyst at Prudential Investments (1997-1998). A portfolio manager and officer of other portfolios in the OppenheimerFunds complex.
Kristin Ketner Pak, Vice President (since 2012) Year of Birth: 1965	Vice President of the Sub-Adviser (since June 2009) and a portfolio manager of the Sub-Adviser (since November 2012). Sector manager for consumer discretionary and consumer staples for the Sub-Adviser’s Main Street Investment Team (since May 2009). Sector manager at RS Investment and Guardian Life Insurance Company. Guardian Life Insurance Company in February 2006 and transitioned to RS Investments in October 2006 in connection with Guardian Life Insurance Company’s acquisition of an interest in RS Investments. Portfolio Manager at Solstice Equity Management (2002-2005); retail analyst at Goldman Sachs (1999-2001); Director of Strategy and Integration at Staples (1997-1999); investment banker at Merrill Lynch (1987-1992 and 1995-1997) and Montgomery Securities (1994-1995). A portfolio manager and officer of other portfolios in the OppenheimerFunds complex.
Magnus Krantz, Vice President (since 2012) Year of Birth: 1967	Vice President of the Sub-Adviser (since May 2009) and a portfolio manager of the Sub-Adviser (since November 2012); sector manager for technology for the Sub-Adviser’s Main Street Investment Team (since May 2009). Prior to joining the Sub-Adviser, Mr. Krantz was a sector manager at RS Investment and Guardian Life Insurance Company. Mr. Krantz joined Guardian Life Insurance Company in December 2005 and transitioned to RS Investments in October 2006 in connection with Guardian Life Insurance Company’s acquisition of an interest in RS Investments. Portfolio manager and analyst at Citigroup Asset Management (1998-2005) and as a consultant at Price Waterhouse (1997-1998). He also served as product development engineer at Newbridge Networks (1993-1996) and as a software engineer at Mitel Corporation (1990-1993). A portfolio manager and officer of other portfolios in the OppenheimerFunds complex.
Adam Weiner, Vice President (since 2012) Year of Birth: 1969	Vice President of the Sub-Adviser (since May 2009) and a portfolio manager of the Sub-Adviser (since November 2012). Sector manager for industrials and materials for the Sub-Adviser’s Main Street Investment Team (since May 2009). Sector manager at RS Investment for industrials and materials (January 2007-April 2009). Director and senior equity analyst at Credit Suisse Asset Management (CSAM) (September 2004-December 2006). Equity analyst at Credit Suisse First Boston 2004-2006 (buy-side) and 1999-2004 (sell-side) and Morgan Stanley (1996-1999); internal auditor at Dun

45         OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

TRUSTEES AND OFFICERS      Unaudited / Continued

Adam Weiner Continued	and Bradstreet (1992-1996). Budget analyst, Information Resources Division of the Executive Office of the President (1990-1992). A portfolio manager and officer of other portfolios in the OppenheimerFunds complex.
Arthur S. Gabinet, Secretary and Chief Legal Officer (since 2011) Year of Birth: 1958	Executive Vice President, Secretary and General Counsel of the Manager (since January 2013); General Counsel OFI SteelPath, Inc. (since January 2013); Executive Vice President (May 2010-December 2012) and General Counsel (since January 2011) of the Sub-Adviser; General Counsel of the Distributor (since January 2011); General Counsel of Centennial Asset Management Corporation (January 2011-December 2012); Executive Vice President (January 2011-December 2012) and General Counsel of HarbourView Asset Management Corporation (since January 2011); Assistant Secretary (since January 2011) and Director (since January 2011) of OppenheimerFunds International Ltd. and OppenheimerFunds plc; Director of Oppenheimer Real Asset Management, Inc. (January 2011-December 2012) and General Counsel (since January 2011); Executive Vice President (January 2011-December 2011) and General Counsel of Shareholder Financial Services, Inc. and Shareholder Services, Inc. (since January 2011); Executive Vice President (January 2011-December 2012) and General Counsel of OFI Private Investments Inc. (since January 2011); Vice President of OppenheimerFunds Legacy Program (January 2011-December 2011); Executive Vice President (January 2011-December 2012) and General Counsel of OFI Institutional Asset Management, Inc. (since January 2011); General Counsel, Asset Management of the Sub-Adviser (May 2010-December 2010); Principal, The Vanguard Group (November 2005-April 2010); District Administrator, U.S. Securities and Exchange Commission (January 2003-October 2005). An officer of 86 portfolios in the OppenheimerFunds complex.
Christina M. Nasta, Vice President and Chief Business Officer (since 2011) Year of Birth: 1973	Senior Vice President of OppenheimerFunds Distributor, Inc. (since January 2013); Senior Vice President of the Sub-Adviser (July 2010-December 2012); Vice President of the Sub-Adviser (January 2003-July 2010); Vice President of OppenheimerFunds Distributor, Inc. (January 2003-July 2010). An officer of 86 portfolios in the OppenheimerFunds complex.
Mark S. Vandehey, Vice President and Chief Compliance Officer (since 2004) Year of Birth: 1950	Senior Vice President and Chief Compliance Officer of the Manager (since January 2013); Chief Compliance Officer of OFI SteelPath, Inc. (since January 2013); Senior Vice President of the Sub-Adviser (March 2004-December 2012); Chief Compliance Officer of the Sub-Adviser, OppenheimerFunds Distributor, Inc., OFI Trust Company, OFI Institutional Asset Management, Inc., Oppenheimer Real Asset Management, Inc., OFI Private Investments, Inc., Harborview Asset Management Corporation, Trinity Investment Management Corporation, and Shareholder Services, Inc. (since March 2004); Vice President of OppenheimerFunds Distributor, Inc., Centennial Asset Management Corporation and Shareholder Services, Inc. (June 1983-December 2012). An officer of 86 portfolios in the OppenheimerFunds complex.
Brian W. Wixted, Treasurer and Principal Financial & Accounting Officer (since 1999) Year of Birth: 1959	Senior Vice President of the Manager (since January 2013); Treasurer of the Sub-Adviser, HarbourView Asset Management Corporation, Shareholder Financial Services, Inc., Shareholder Services, Inc., and Oppenheimer Real Asset Management, Inc. (March 1999-June 2008), OFI Private Investments, Inc. (March 2000-June 2008), OppenheimerFunds International Ltd. and OppenheimerFunds plc (since May 2000), OFI Institutional Asset Management, Inc. (November 2000-June 2008), and OppenheimerFunds Legacy Program (charitable trust program established by the Sub-Adviser) (June 2003-December 2011); Treasurer and Chief Financial Officer of OFI Trust Company (since May 2000); Assistant Treasurer of Oppenheimer Acquisition Corporation (March 1999-June 2008). An officer of 86 portfolios in the OppenheimerFunds complex.

46      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

The Fund’s Statement of Additional Information contains additional information about

the Fund’s Trustees and Officers and is available without charge, upon request, by calling

1.800.CALL OPP (225.5677).

47         OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

OPPENHEIMERMAIN STREET SMALL- & MID-CAP FUND

Manager	OFI Global Asset Management, Inc.
Sub-Adviser	OppenheimerFunds, Inc.
Distributor	OppenheimerFunds Distributor, Inc.
Transfer and Shareholder Servicing Agent	OFI Global Asset Management, Inc.
Sub-Transfer Agent	Shareholder Services, Inc. DBA OppenheimerFunds Services
Independent Registered Public Accounting Firm	KPMG LLP
Legal Counsel	K&L Gates LLP

© 2013 OppenheimerFunds, Inc. All rights reserved.

48      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

PRIVACY POLICY NOTICE

As an Oppenheimer fund shareholder, you are entitled to know how we protect your personal information and how we limit its disclosure.

Information Sources

We obtain nonpublic personal information about our shareholders from the following sources:

— Applications or other forms

— When you create a user ID and password for online account access

— When you enroll in eDocs Direct, our electronic document delivery service

— Your transactions with us, our affiliates or others

— A software program on our website, often referred to as a “cookie,” which indicates which parts of our site you’ve visited

— When you set up challenge questions to reset your password online

If you visit oppenheimerfunds.com and do not log on to the secure account information areas, we do not obtain any personal information about you. When you do log on to a secure area, we do obtain your user ID and password to identify you. We also use this information to provide you with products and services you have requested, to inform you about products and services that you may be interested in and assist you in other ways.

We do not collect personal information through our website unless you willingly provide it to us, either directly by email or in those areas of the website that request information. In order to update your personal information (including your mailing address, email address and phone number) you must first log on and visit your user profile.

If you have set your browser to warn you before accepting cookies, you will receive the warning message with each cookie. You can refuse cookies by turning them off in your browser. However, doing so may limit your access to certain sections of our website.

We use cookies to help us improve and manage our website. For example, cookies help us recognize new versus repeat visitors to the site, track the pages visited, and enable some special features on the website. This data helps us provide a better service for our website visitors.

Protection of Information

We do not disclose any non-public personal information (such as names on a customer list) about current or former customers to anyone, except as permitted by law.

Disclosure of Information

We send your financial advisor (as designated by you) copies of confirmations, account statements and other documents reporting activity in your fund accounts. We may also use details about you and your investments to help us, our financial service affiliates, or firms that jointly market their financial products and services with ours, to better serve your investment needs or suggest financial services or educational material that may be of interest to you. If this requires us to provide you with an opportunity to “opt in” or “opt out” of such information sharing with a firm not affiliated with us, you will receive notification on how to do so, before any such sharing takes place.

Right of Refusal

We will not disclose your personal information to unaffiliated third parties (except as permitted by law), unless we first offer you a reasonable opportunity to refuse or “opt out” of such disclosure.

49      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

PRIVACY POLICY NOTICE     (Continued)

Internet Security and Encryption

In general, the email services provided by our website are encrypted and provide a secure and private means of communication with us. To protect your own privacy, confidential and/or personal information should only be communicated via email when you are advised that you are using a secure website.

As a security measure, we do not include personal or account information in non-secure emails, and we advise you not to send such information to us in non-secure emails. Instead, you may take advantage of the secure features of our website to encrypt your email correspondence. To do this, you will need to use a browser that supports Secure Sockets Layer (SSL) protocol.

We do not guarantee or warrant that any part of our website, including files available for download, are free of viruses or other harmful code. It is your responsibility to take appropriate precautions, such as use of an anti-virus software package, to protect your computer hardware and software.

— All transactions, including redemptions, exchanges and purchases, are secured by SSL and 128-bit encryption. SSL is used to establish a secure connection between your PC and OppenheimerFunds’ server. It transmits information in an encrypted and scrambled format.

— Encryption is achieved through an electronic scrambling technology that uses a “key” to code and then decode the data. Encryption acts like the cable converter box you may have on your television set. It scrambles data with a secret code so that no one can make sense of it while it is being transmitted. When the data reaches its destination, the same software unscrambles the data.

— You can exit the secure area by either closing your browser, or for added security, you can use the Log Out button before you close your browser.

Other Security Measures

We maintain physical, electronic and procedural safeguards to protect your personal account information. Our employees and agents have access to that information only so that they may offer you products or provide services, for example, when responding to your account questions.

How You Can Help

You can also do your part to keep your account information private and to prevent unauthorized transactions. If you obtain a user ID and password for your account, do not allow it to be used by anyone else. Also, take special precautions when accessing your account on a computer used by others.

Who We Are

This joint notice describes the privacy policies of the Oppenheimer funds, OppenheimerFunds, Inc., and each of its financial institution subsidiaries, the trustee of OppenheimerFunds Individual Retirement Accounts (IRAs) and the custodian of the OppenheimerFunds 403(b)(7) tax sheltered custodial accounts. It applies to all Oppenheimer fund accounts you presently have, or may open in the future, using your Social Security number—whether or not you remain a shareholder of our funds. This notice was last updated November 2012. In the event it is updated or changed, we will post an updated notice on our website at oppenheimerfunds.com. If you have any questions about these privacy policies, write to us at P.O. Box 5270, Denver, CO 80217-5270, email us by clicking on the Contact Us section of our website at oppenheimerfunds.com or call us at 1.800.CALL OPP (225.5677).

50      OPPENHEIMER MAIN STREET SMALL- & MID-CAP FUND

Item 2. Code of Ethics.

The registrant has adopted a code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller or persons performing similar functions.

Item 3. Audit Committee Financial Expert.

The Board of Trustees of the registrant has determined that F. William Marshall, Jr., the Chairman of the Board’s Audit Committee, is the audit committee financial expert and that Mr. Marshall is “independent” for purposes of this Item 3.

Item 4. Principal Accountant Fees and Services.

(a) Audit Fees

The principal accountant for the audit of the registrant’s annual financial statements billed $30,900 in fiscal 2013 and $30,300 in fiscal 2012.

(b) Audit-Related Fees

The principal accountant for the audit of the registrant’s annual financial statements billed no such fees in fiscal 2013 and no such fees in fiscal 2012.

The principal accountant for the audit of the registrant’s annual financial statements billed $530,330 in fiscal 2013 and $380,556 in fiscal 2012 to the registrant’s investment adviser or any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant.

Such services include: Internal control reviews, compliance procedures, GIPS attestation procedures, internal audit training, surprise exams, system conversion testing, and corporate restructuring.

(c) Tax Fees

The principal accountant for the audit of the registrant’s annual financial statements billed no such fees in fiscal 2013 and no such fees in fiscal 2012.

The principal accountant for the audit of the registrant’s annual financial statements billed $443,073 in fiscal 2013 and $317,764 in fiscal 2012 to the registrant’s investment adviser or any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant.

Such services include: tax compliance, tax planning and tax advice. Tax compliance generally involves preparation of original and amended tax returns, claims for a refund and tax payment-planning services. Tax planning and tax advice includes assistance with tax audits and appeals, tax advice related to mergers and acquisitions and requests for rulings or technical advice from taxing authorities.

(d) All Other Fees

The principal accountant for the audit of the registrant’s annual financial statements billed no such fees in fiscal 2013 and no such fees in fiscal 2012.

The principal accountant for the audit of the registrant’s annual financial statements billed no such fees in fiscal 2013 and no such fees in fiscal 2012 to the registrant’s investment adviser or any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant.

Such fees would include the cost to the principal accountant of attending audit committee meetings and consultations regarding the registrant’s retirement plan with respect to its Trustees.

(e) (1) During its regularly scheduled periodic meetings, the registrant’s audit committee will pre-approve all audit, audit-related, tax and other services to be provided by the principal accountants of the registrant.

The audit committee has delegated pre-approval authority to its Chairman for any subsequent new engagements that arise between regularly scheduled meeting dates provided that any fees such pre-approved are presented to the audit committee at its next regularly scheduled meeting.

Under applicable laws, pre-approval of non-audit services may be waived provided that: 1) the aggregate amount of all such services provided constitutes no more than five percent of the total amount of fees paid by the registrant to its principal accountant during the fiscal year in which services are provided 2) such services were not recognized by the registrant at the time of engagement as non-audit services and 3) such services are promptly brought to the attention of the audit committee of the registrant and approved prior to the completion of the audit.

(2) 0%

(f) Not applicable as less than 50%.

(g) The principal accountant for the audit of the registrant’s annual financial statements billed $973,403 in fiscal 2013 and $698,320 in fiscal 2012 to the registrant and the registrant’s investment adviser or any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant related to non-audit fees. Those billings did not include any prohibited non-audit services as defined by the Securities Exchange Act of 1934.

(h) The registrant’s audit committee of the board of Trustees has considered whether the provision of non-audit services that were rendered to the registrant’s investment adviser, and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant’s independence. No such services were rendered.

Item 5. Audit Committee of Listed Registrants

Not applicable.

Item 6. Schedule of Investments.

a) Not applicable. The complete schedule of investments is included in Item 1 of this Form N-CSR.

b) Not applicable.

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies.

Not applicable.

Item 8. Portfolio Managers of Closed-End Management Investment Companies.

Not applicable.

Item 9. Purchases of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers.

Not applicable.

Item 10. Submission of Matters to a Vote of Security Holders.

The Fund’s Governance Committee Provisions with Respect to Nominations of Directors/Trustees to the Respective Boards

None

Item 11. Controls and Procedures.

Based on their evaluation of the registrant’s disclosure controls and procedures (as defined in rule 30a-3(c) under the Investment Company Act of 1940 (17 CFR 270.30a-3(c)) as of 6/28/2013, the registrant’s principal executive officer and principal financial officer found the registrant’s disclosure controls and procedures to provide reasonable assurances that information required to be disclosed by the registrant in the reports that it files under the Securities Exchange Act of 1934 (a) is accumulated and communicated to registrant’s management, including its principal executive officer and principal financial officer, to allow timely decisions regarding required disclosure, and (b) is recorded, processed, summarized and reported, within the time periods specified in the rules and forms adopted by the U.S. Securities and Exchange Commission.

There have been no changes in the registrant’s internal controls over financial reporting that occurred during the registrant’s second fiscal quarter of the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12. Exhibits.

(a) (1) Exhibit attached hereto.

(2) Exhibits attached hereto.

(3) Not applicable.

(b) Exhibit attached hereto.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Oppenheimer Main Street Small- & Mid- Cap Fund

By:	/s/ William F. Glavin, Jr.
	William F. Glavin, Jr.
	Principal Executive Officer
Date: 8/9/2013

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By:	/s/ William F. Glavin, Jr.
	William F. Glavin, Jr.
	Principal Executive Officer
Date: 8/9/2013

By:	/s/ Brian W. Wixted
	Brian W. Wixted
	Principal Financial Officer
Date: 8/9/2013

EX-99.CODE ETH

CODE OF ETHICS

FOR PRINCIPAL EXECUTIVE AND FINANCIAL OFFICERS

OF THE OPPENHEIMER FUNDS

AND OPPENHEIMERFUNDS, INC.

This Code of Ethics for Principal Executive and Financial Officers (referred to in this document as the “Code”) has been adopted by each of the investment companies for which OppenheimerFunds, Inc. or one of its subsidiaries or affiliates (referred to collectively in this document as “OFI”) acts as investment adviser (individually, a “Fund” and collectively, the “Funds”), and by OFI to effectuate compliance with Section 406 under the Sarbanes-Oxley Act of 2002 and the rules adopted to implement Section 406.

This Code applies to OFI’s and each Fund’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions (“Covered Officers”). A listing of positions currently within the ambit of Covered Officers is attached as Exhibit A.¹

1. Purpose of the Code

This Code sets forth standards and procedures that are reasonably designed to deter wrongdoing and promote:

• honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships;

• full, fair, accurate, timely, and understandable disclosure in reports and documents that a Fund files with, or submits to, the U.S. Securities and Exchange Commission (“SEC”) and in other public communications made by the Fund;

• compliance with applicable governmental laws, rules and regulations;

• the prompt internal reporting of violations of this Code to the Code Administrator identified below; and

• accountability for adherence to this Code.

In general, the principles that govern honest and ethical conduct, including the avoidance of conflicts of interest between personal and professional relationships, reflect, at the minimum, the following: (1) the duty at all times in performing any responsibilities as a Fund financial officer, controller, accountant or principal executive officer to place the interests of the Funds ahead of personal interests; (2) the fundamental standard that Covered Officers should not take inappropriate advantage of their positions; (3) the duty to assure that a Fund’s financial statements and reports to its shareholders are prepared honestly and accurately in accordance with applicable rules, regulations and accounting standards; and (4) the duty to conduct the Funds’ business and affairs in an honest and ethical manner. Each Covered Officer should be sensitive to situations that may give rise to actual as well as apparent conflicts of interest.

¹  The obligations imposed by this Code on Covered Officers are separate from and in addition to any obligations that may be imposed on such persons as Covered Persons under the Code of Ethics adopted by OFI and the Funds under Rule 17j-1 of the Investment Company Act of 1940, as amended and any other code of conduct applicable to Covered Officers in whatever capacity they serve. This Code does not incorporate by reference any provisions of the Rule 17j-1 Code of Ethics and accordingly, any violations or waivers granted under the Rule 17j-1 Code of Ethics will not be considered a violation or waiver under this Code.

It is acknowledged that, as a result of the contractual relationship between each Fund and OFI, of which the Covered Officers are also officers or employees, and subject to OFI’s fiduciary duties to each Fund, the Covered Officers will, in the normal course of their duties, be involved in establishing policies and implementing decisions that will have different effects on OFI and the Funds. It is further acknowledged that the participation of the Covered Officers in such activities is inherent in the contractual relationship between each Fund and OFI and is consistent with the expectations of the Board of Trustees/Directors of the performance by the Covered Officers of their duties as officers of the Funds.

2. Prohibitions

The specific provisions and reporting requirements of this Code are concerned primarily with promoting honest and ethical conduct and avoiding conflicts of interest in personal and professional relationships. No Covered Officer may use information concerning the business and affairs of a Fund, including the investment intentions of a Fund, or use his or her ability to influence such investment intentions, for personal gain to himself or herself, his or her family or friends or any other person or in a manner detrimental to the interests of a Fund or its shareholders.

No Covered Officer may use his or her personal influence or personal relationships to influence the preparation and issuance of financial reports of a Fund whereby the Covered Officer would benefit personally to the detriment of the Fund and its shareholders.

No Covered Officer shall intentionally for any reason take any action or fail to take any action in connection with his or her official acts on behalf of a Fund that causes the Fund to violate applicable laws, rules and regulations.

No Covered Officer shall, in connection with carrying out his or her official duties and responsibilities on behalf of a Fund:

(i) employ any device, scheme or artifice to defraud a Fund or its shareholders;

(ii) intentionally cause a Fund to make any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements made, in light of the circumstances under which they are made, not misleading in its official documents, regulatory filings, financial statements or communications to the public;

(iii) engage in any act, practice, or course of business which operates or would operate as a fraud or deceit upon any Fund or its shareholders;

(iv) engage in any manipulative practice with respect to any Fund;

(v) use his or her personal influence or personal relationships to influence any business decision, investment decisions, or financial reporting by a Fund whereby the Covered Officer would benefit personally to the detriment of the Fund or its shareholders;

(vi) intentionally cause a Fund to fail to comply with applicable laws, rules and regulations, including failure to comply with the requirement of full, fair, accurate, understandable and timely disclosure in reports and documents that a Fund files with, or submits to, the SEC and in other public communications made by the Fund;

(vii) intentionally mislead or omit to provide material information to the Fund’s independent auditors or to the Board of Trustees/Directors or the officers of the Fund or its investment adviser in connection with financial reporting matters;

(viii) fail to notify the Code Administrator or the Chief Executive Officer of the Fund or its investment adviser promptly if he or she becomes aware of any existing or potential violations of this Code or applicable laws;

(ix) retaliate against others for, or otherwise discourage the reporting of, actual or apparent violations of this Code; or

(x) fails to acknowledge or certify compliance with this Code if requested to do so.

3. Reports of Conflicts of Interests

If a Covered Officer becomes aware of a conflict of interest under this Code or, to the Covered Officer’s reasonable belief, the appearance of one, he or she must immediately report the matter to the Code’s Administrator. If the Code Administrator is involved or believed to be involved in the conflict of interest or appearance of conflict of interest, the Covered Officer shall report the matter directly to the OFI’s Chief Executive Officer.

Upon receipt of a report of a conflict, the Code Administrator will take prompt steps to determine whether a conflict of interest exists. If the Code Administrator determines that an actual conflict of interest exists, the Code Administrator will take steps to resolve the conflict. If the Code Administrator determines that the appearance of a conflict exists, the Code Administrator will take appropriate steps to remedy such appearance. If the Code Administrator determines that no conflict or appearance of a conflict exists, the Code Administrator shall meet with the Covered Officer to advise him or her of such finding and of his or her reason for taking no action. In lieu of determining whether a conflict or appearance of conflict exists, the Code Administrator may in his or her discretion refer the matter to the Fund’s Board of Trustees/Directors.

4. Waivers

Any Covered Officer requesting a waiver of any of the provisions of this Code must submit a written request for such waiver to the Code Administrator, setting forth the basis of such request and all necessary facts upon which such request can be evaluated. The Code Administrator shall review such request and make a written determination thereon, which shall be binding. The Code Administrator may in reviewing such request, consult at his discretion with legal counsel to OFI or to the Fund.

In determining whether to waive any of the provisions of this Code, the Code Administrator shall consider whether the proposed waiver:

(i) is prohibited by this Code;

(ii) is consistent with honest and ethical conduct; and

(iii) will result in a conflict of interest between the Covered Officer’s personal and professional obligations to a Fund.

In lieu of determining whether to grant a waiver, the Code Administrator in his or her discretion may refer the matter to the appropriate Fund’s Board of Trustees/Directors.

5. Reporting Requirements

(a) Each Covered Officer shall, upon becoming subject to this Code, be provided with a copy of this Code and shall affirm in writing that he or she has received, read, understands and shall adhere to this Code.

(b) At least annually, all Covered Officers shall be provided with a copy of this Code and shall certify that they have read and understand this Code and recognize that they are subject thereto.

(c) At least annually, all Covered Officers shall certify that they have complied with the requirements of this Code and that they have disclosed or reported any violations of this Code to the Code Administrator or the Chief Executive Officer of the Fund or its investment adviser.

(d) The Code Administrator shall submit a quarterly report to the Board of Trustees/Directors of each Fund containing (i) a description of any report of a conflict of interest or apparent conflict and the disposition thereof; (ii) a description of any request for a waiver from this Code and the disposition thereof; (iii) any violation of the Code that has been reported or found and the sanction imposed; (iv) interpretations issued under the Code by the Code Administrator; and (v) any other significant information arising under the Code including any proposed amendments.

(e) Each Covered Officer shall notify the Code Administrator promptly if he or she knows of or has a reasonable belief that any violation of this Code has occurred or is likely to occur. Failure to do so is itself a violation of this Code.

(f) Any changes to or waivers of this Code, including “implicit” waivers as defined in applicable SEC rules, will, to the extent required, be disclosed by the Code Administrator or his or her designee as provided by applicable SEC rules.²

6. Annual Review

At least annually, the Board of Trustees/Directors of each Fund shall review the Code and consider whether any amendments are necessary or desirable.

7. Sanctions

Any violation of this Code of Ethics shall be subject to the imposition of such sanctions by OFI as may be deemed appropriate under the circumstances to achieve the purposes of this Code and may include, without limitation, a letter of censure, suspension from employment or termination of employment, in the sole discretion of OFI.

8. Administration and Construction

(a) The administration of this Code of Ethics shall be the responsibility of OFI’s General Counsel or his designee as the “Code Administrator” of this Code, acting under the terms of this Code and the oversight of the Trustees/Directors of the Funds.

(b) The duties of such Code Administrator will include:

(i) Continuous maintenance of a current list of the names of all Covered Officers;

(ii) Furnishing all Covered Officers a copy of this Code and initially and periodically informing them of their duties and obligations thereunder;

(iii) Maintaining or supervising the maintenance of all records required by this Code, including records of waivers granted hereunder;

(iv) Issuing interpretations of this Code which appear to the Code Administrator to be consistent with the objectives of this Code and any applicable laws or regulations;

(v) Conducting such inspections or investigations as shall reasonably be required to detect and report any violations of this Code, with his or her recommendations, to the Chief Executive Officer of OFI and to the Trustees/Directors of the affected Fund(s) or any committee appointed by them to deal with such information; and Periodically conducting educational training programs as needed to explain and reinforce the terms of this Code.

(c) In carrying out the duties and responsibilities described under this Code, the Code Administrator may consult with legal counsel, who may include legal counsel to the applicable Funds, and such other persons as the Administrator shall deem necessary or desirable. The Code Administrator shall be protected from any liability hereunder or under any applicable law, rule or regulation, for decisions made in good faith based upon his or her reasonable judgment.

²  An “implicit waiver” is the failure to take action within a reasonable period of time regarding a material departure from a provision of this Code that has been made known to the General Counsel, the Code Administrator, and an executive officer of the Fund or OFI.

9. Required Records

The Administrator shall maintain and cause to be maintained in an easily accessible place, the following records for the period required by applicable SEC rules (currently six years following the end of the fiscal year of OFI in which the applicable event or report occurred):

(a) A copy of any Code which has been in effect during the period;

(b) A record of any violation of any such Code and of any action taken as a result of such violation, during the period;

(c) A copy of each annual report pursuant to the Code made by a Covered Officer during the period;

(d) A copy of each report made by the Code Administrator pursuant to this Code during the period;

(e) A list of all Covered Officers who are or have been required to make reports pursuant to this Code during the period, plus those person(s) who are or were responsible for reviewing these reports;

(f) A record of any request to waive any requirement of this Code, the decision thereon and the reasons supporting the decision; and

(g) A record of any report of any conflict of interest or appearance of a conflict of interest received by the Code Administrator or discovered by the Code Administrator during the period, the decision thereon and the reasons supporting the decision.

10. Amendments and Modifications

Other than non-substantive or administrative changes, this Code may not be amended or modified unless approved or ratified by the Board of Trustees/Directors of each Fund.

11. Confidentiality.

This Code is identified for the internal use of the Funds and OFI. Reports and records prepared or maintained under this Code are considered confidential and shall be maintained and protected accordingly to the extent permitted by applicable laws, rules and regulations. Except as otherwise required by law or this Code, such matters shall not be disclosed to anyone other than the Trustees/Directors of the affected Fund(s) and their counsel, the independent auditors of the affected Funds and/or OFI, and to OFI, except as such disclosure may be required pursuant to applicable judicial or regulatory process.

Dated as of: June 25, 2003, as revised August 30, 2006 and further revised as of March 5, 2010.

Exhibit A

Positions Covered by this Code of Ethics for Principal Executive and Financial Officers*

Each Oppenheimer fund

President (Principal Executive Officer)

Treasurer (Principal Financial Officer)

OFI

President and Chief Executive Officer (Principal Executive Officer)

Chief Financial Officer and Treasurer (Principal Financial Officer)

* There are no other positions with the Funds or OFI who perform similar functions to those listed above.

EX-99.CERT

Exhibit 99.CERT

Section 302 Certifications

CERTIFICATIONS

I, William F. Glavin, Jr., certify that:

1. I have reviewed this report on Form N-CSR of Oppenheimer Main Street Small- & Mid- Cap Fund;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, changes in net assets, and cash flows (if the financial statements are required to include a statement of cash flows) of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of a date within 90 days prior to the filing date of this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed to the registrant’s auditors and the audit committee of the registrant’s board of Trustees (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: 8/9/2013

/s/ William F. Glavin, Jr.

William F. Glavin, Jr.

Principal Executive Officer

Exhibit 99.CERT

Section 302 Certifications

CERTIFICATIONS

I, Brian W. Wixted, certify that:

1. I have reviewed this report on Form N-CSR of Oppenheimer Main Street Small- & Mid- Cap Fund;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, changes in net assets, and cash flows (if the financial statements are required to include a statement of cash flows) of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of a date within 90 days prior to the filing date of this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed to the registrant’s auditors and the audit committee of the registrant’s board of Trustees (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: 8/9/2013

/s/ Brian W. Wixted

Brian W. Wixted

Principal Financial Officer

EX-99.906CERT

EX-99.906CERT

Section 906 Certifications

CERTIFICATION PURSUANT TO 18 U.S.C SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

William F. Glavin, Jr., Principal Executive Officer, and Brian W. Wixted, Principal Financial Officer, of Oppenheimer Main Street Small- & Mid- Cap Fund (the “Registrant”), each certify to the best of his knowledge that:

1. The Registrant’s periodic report on Form N-CSR for the period ended 6/28/2013 (the “Form N-CSR”) fully complies with the requirements of Section 15(d) of the Securities Exchange Act of 1934, as amended; and

2. The information contained in the Form N-CSR fairly presents, in all material respects, the financial condition and results of operations of the Registrant. This certification is being furnished to the Commission solely pursuant to 18 U.S.C. § 1350 and is not being filed as part of the Form N-CSR filed with the Commission.

Principal Executive Officer	Principal Financial Officer
Oppenheimer Main Street Small- & Mid- Cap Fund	Oppenheimer Main Street Small- & Mid- Cap Fund
/s/ William F. Glavin, Jr.	/s/ Brian W. Wixted
William F. Glavin, Jr.	Brian W. Wixted
Date: 8/9/2013	Date: 8/9/2013