Oppenheimer Main Street Mid Cap Fund

N-CSR 1 d35431dncsr.htm OPPENHEIMER MAIN STREET MID CAP FUND Oppenheimer Main Street Mid Cap Fund

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 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.

225 Liberty Street, 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: 6/30/2015

Item 1.

Reports to Stockholders.

LOGO

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			37

Federal Income Tax Information			38

Portfolio Proxy Voting Policies and Procedures; Updates to Statement of Investments			39

Trustees and Officers			40

Privacy Policy Notice			48

Class A Shares

AVERAGE ANNUAL TOTAL RETURNS AT 6/30/15


	Class A Shares of the Fund
	Without Sales Charge	With Sales Charge	Russell Midcap Index
1-Year	5.58 %	-0.49 %	6.63 %
5-Year	16.83	15.46	18.23
10-Year	8.39	7.75	9.40

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. 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).

2 OPPENHEIMER MAIN STREET MID CAP FUND

Fund Performance Discussion

The Fund’s Class A shares (without sales charge) produced a return of 5.58% during the reporting period, underperforming the Russell Midcap Index (the “Index”), which returned 6.63% during the same period. The bulk of the Fund’s underperformance occurred within the industrials and materials sectors, due to less favorable stock selection. The Fund outperformed the Index within the health care sector due to stock selection and an overweight position, and in the information technology sector due to stock selection. Stock selection in the consumer discretionary sector and an underweight position in the utilities sector outperformed the Index to a lesser degree.

MARKET OVERVIEW

In 2014, domestic equity — as an asset class — distinguished itself as stocks appreciated in value across all capitalizations. During the year, the U.S. economy provided a favorable backdrop for the positive performance of equities with steady, albeit modest growth, continued little wage inflation, and interest rates that remained low — in fact, well below initial expectations. Under these economic conditions, many companies were able to demonstrate ongoing improvement with the majority beating market expectations

— on both the top and bottom lines. The ride throughout the year, however, was anything but smooth. Macro influences — particularly the strengthening dollar, flattening yield curve, and tumbling oil prices — played a significant role in determining which equities did and did not perform well. Accommodation by the Federal Reserve (the “Fed”) — which officially ended its bond-buying stimulus program in October — helped to fuel demand for high dividend paying stocks such as utilities and real estate

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

LOGO

3 OPPENHEIMER MAIN STREET MID CAP FUND

investment trusts (REITs). A step-up in merger and acquisition (M&A) activity — spurred on by the desire to relocate to advantageous low tax jurisdictions — boosted stocks primarily in the health care sector. But not all was rosy. The Fed’s accommodative behavior proved a headwind for many financials as long yields declined — hurting the profitability of banks. The strengthening U.S. dollar also proved a headwind — especially for multi-national companies where translation from local currencies to the U.S. dollar negatively impacted the bottom line. Consequently, stocks with international businesses broadly underperformed stocks with mostly domestic exposure.

Geopolitical risks — mostly concentrated in Ukraine and Russia, combined with the ever-present turmoil in the Middle East — caused investors to fret resulting in, at times, quite the roller coaster ride. Add to this the fact that growth outside of the U.S. was anemic, at best, leading investors to worry intermittently about the global outlook and its impact on domestic stocks. Though volatility remained below historical averages, these issues caused it to spike on a number of occasions during 2014.

The first half of 2015 was largely a continuation of the back half of 2014. Foreign exchange headwinds, declining energy prices, questions as to when the Fed would finally move to raise interest rates, and Greece’s debt crisis dominated the headlines.

Energy continued to struggle as oil prices fell. Other commodity prices sputtered also — negatively impacting many materials stocks. With falling commodity prices, capital spending plans have been reined-in and this, in combination with a faltering global economic outlook, resulted in weak performance by many industrials stocks. After having been among the best performing stocks in 2014, utilities, which are very sensitive to interest rate expectations, faced pressures as investors became increasingly convinced the Fed would act this year to raise rates. Health care stocks continued to be a bright spot. In addition to high levels of M&A activity, investors’ appetite for risk has increased, resulting in a speculative market concentrated largely in a narrow group of stocks, especially biotechnology companies. Despite lofty valuations, these stocks continued to perform well. However, the question becomes for how much longer. Consumer discretionary stocks have also performed well recently reflecting the increased conviction that the U.S. economic recovery will be sustained at moderate levels.

FUND REVIEW

Top performing stocks this reporting period included Skyworks Solutions, Inc., Centene Corp. and Salix Pharmaceuticals, Ltd. Skyworks Solutions is a supplier of analog semiconductors to the wireless industry. The company’s stock benefited from strong demand for its products, in addition to the successful launch of Apple’s iPhone 6, on which Skyworks provides chips. Centene is a

4 OPPENHEIMER MAIN STREET MID CAP FUND

multi-line managed care provider of Medicaid programs that continued to benefit from the tailwind provided by the Affordable Care Act. Consequently, results exceeded expectations and investor sentiment improved—leading to a rising stock price. We continue to view Centene as a core holding and expect good visibility on accelerating earnings growth. The stock of Salix, a developer of drugs aimed at treating gastrointestinal diseases, performed well as Valeant acquired the company for $173 per share in cash.

Detractors from performance this reporting period included Noble Energy, Inc., Genworth Financial, Inc. and NOW, Inc. Noble has a high sensitivity to oil price changes as it has significant exploration and production operations globally. Growth projections are expected to decline as the company adjusts both its cash flow expectations and balance sheet to reflect a diminished outlook for global energy prices. We have maintained our position and continue to have confidence in management’s ability to execute well as of the end of the reporting period. Genworth, which provides insurance for the life, mortgage, and long-term care markets, disappointed investors when it reported third quarter results. Management announced a larger than projected charge to reflect a step-up in claims from holders of its long-term care policies. Additionally, the company disclosed that it would conduct a comprehensive review of all policies — spooking investors further. We exited our position during the reporting period. NOW

distributes oil-drilling equipment globally. Similar to other energy suppliers, NOW’s management lowered its future outlook to reflect the slowdown in customer spending spurred by the fall in oil prices. By period end, we have reduced our holdings because of a diminished outlook for spending by its customers.

STRATEGY & OUTLOOK

While financial engineering, as exemplified by the robust repurchase of shares and a step-up in M&A activities, will augment earnings per share growth in the short term, neither lead to long-term growth. These behaviors, though rational due to the supply of “cheap” money resulting from the easy monetary policies across most Central Banks globally, do not lead to sustainable fundamental economic improvements. We believe only real investments, such as capital spending and research and development, ultimately lead to viable growth over the longer run. These issues remain a concern of the Main Street team and we continue to emphasize investing in companies that are effectively allocating capital for both short-term and long-term sustainable fundamental growth.

We remain alert to disruption—both through product innovation and, increasingly, due to business model and/or process dislocations. Examples include Amazon’s dramatic impact on how goods and services are sold to customers, and how the Affordable Care Act is changing the winners and losers within health care. These disruptors pose both

5 OPPENHEIMER MAIN STREET MID CAP FUND

threats and opportunities, and our research is increasingly focused on distinguishing between the two.

Though equity market valuations are a bit above historical averages at period end, a higher valuation level might be justified should profitability remain strong and interest rates remain low. Given our outlook that inflation will remain tame and, therefore, interest rates are unlikely to rise dramatically over the immediate future, we are not expecting a significant contraction in the market’s multiple; however, there is little margin for error.

Regardless, we remain focused on seeking to build an “all weather” portfolio by targeting companies we believe have: 1) sustainable competitive advantages; 2) skilled management with a proven track record of executing effectively; and 3) financial resources with the potential to generate improving profitability, gain market share, and/or return significant cash to shareholders. During times of volatile or slow economic growth such companies frequently 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 in seeking to generate superior long-term performance.

LOGO

Raymond Anello, CFA

Portfolio Manager

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

6 OPPENHEIMER MAIN STREET MID CAP FUND

Top Holdings and Allocations

TOP TEN COMMON STOCK HOLDINGS


Universal Health Services, Inc., Cl. B	2.8	%
Centene Corp.	2.5
FNF Group	2.5
L-3 Communications Holdings, Inc.	2.4
CME Group, Inc., Cl. A	2.3
Envision Healthcare Holdings, Inc.	2.2
Tyco International plc	2.1
Dana Holding Corp.	2.1
Alcoa, Inc.	2.1
Mid-America Apartment Communities, Inc.	2.1

Portfolio holdings and allocations are subject to change. Percentages are as of June 30, 2015, and are based on net assets. For more current Fund holdings, please visit oppenheimerfunds.com.

TOP TEN COMMON STOCK INDUSTRIES


Health Care Providers & Services	9.8	%
Real Estate Investment Trusts (REITs)	8.5
Specialty Retail	6.2
Software	5.6
Oil, Gas & Consumable Fuels	4.8
Insurance	4.5
Consumer Finance	3.7
Semiconductors & Semiconductor Equipment	3.7
Metals & Mining	3.6
Health Care Equipment & Supplies	3.6

Portfolio holdings and allocations are subject to change. Percentages are as of June 30, 2015, and are based on net assets.

SECTOR ALLOCATION

LOGO

Portfolio holdings and allocations are subject to change. Percentages are as of June 30, 2015, and are based on the total market value of common stocks.

7 OPPENHEIMER MAIN STREET MID CAP FUND

Share Class Performance

AVERAGE ANNUAL TOTAL RETURNS WITHOUT SALES CHARGE AS OF 6/30/15


	Inception Date	1-Year	5-Year	10-Year
Class A (OPMSX)	8/2/99	5.58%	16.83%	8.39%
Class B (OPMBX)	8/2/99	4.78%	15.89%	7.90%
Class C (OPMCX)	8/2/99	4.78%	15.96%	7.59%
Class I (OPMIX)	10/26/12	6.08%	19.81%*	N/A
Class R (OPMNX)	3/1/01	5.33%	16.53%	8.09%
Class Y (OPMYX)	8/2/99	5.86%	17.23%	8.81%

AVERAGE ANNUAL TOTAL RETURNS WITH SALES CHARGE AS OF 6/30/15


	Inception Date	1-Year	5-Year	10-Year
Class A (OPMSX)	8/2/99	-0.49%	15.46%	7.75%
Class B (OPMBX)	8/2/99	0.35%	15.67%	7.90%
Class C (OPMCX)	8/2/99	3.90%	15.96%	7.59%
Class I (OPMIX)	10/26/12	6.08%	19.81%*	N/A
Class R (OPMNX)	3/1/01	4.43%	16.53%	8.09%
Class Y (OPMYX)	8/2/99	5.86%	17.23%	8.81%

*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 shares, the contingent deferred sales charge (“CDSC”) of 1% for the 1-year period. Prior to 7/1/14, Class R shares were named Class N shares. Beginning 7/1/14, new purchases of Class R shares will no longer be subject to a CDSC upon redemption (any CDSC will remain in effect for purchases prior to 7/1/14).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.

The Fund’s performance is compared to the performance of the Russell Midcap Index. The Russell Midcap Index measures the performance of the mid-cap segment of the U.S. equity universe. The Index is unmanaged and cannot be purchased directly by investors. While index comparisons may be useful to provide a benchmark for the Fund’s performance, it must be noted that the Fund’s investments are not limited to the investments comprising the Index. 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

8 OPPENHEIMER MAIN STREET MID CAP FUND

Fund. The Fund’s performance reflects the effects of the Fund's business and operating expenses.

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 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 and/or 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 30, 2015.

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 6 Months Ended June 30, 2015” 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 Fund’s 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). 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 MID CAP FUND


Actual	Beginning Account Value January 1, 2015	Ending Account Value June 30, 2015	Expenses Paid During 6 Months Ended June 30, 2015
Class A	$ 1,000.00	$ 1,022.00	$ 5.53
Class B	1,000.00	1,018.00	9.30
Class C	1,000.00	1,018.20	9.30
Class I	1,000.00	1,024.40	3.32
Class R	1,000.00	1,020.80	6.79
Class Y	1,000.00	1,023.40	4.27

Hypothetical (5% return before expenses)
Class A	1,000.00	1,019.34	5.52
Class B	1,000.00	1,015.62	9.29
Class C	1,000.00	1,015.62	9.29
Class I	1,000.00	1,021.52	3.31
Class R	1,000.00	1,018.10	6.78
Class Y	1,000.00	1,020.58	4.27

Expenses are equal to the Fund’s annualized expense ratio for that class, multiplied by the average account value over the period, multiplied by 181/365 (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 30, 2015 are as follows:


Class	Expense Ratios
Class A		1.10	%
Class B		1.85
Class C		1.85
Class I		0.66
Class R		1.35
Class Y		0.85

The expense ratios reflect voluntary and/or contractual waivers and/or reimbursements of expenses by the Fund’s Manager. 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 MID CAP FUND

STATEMENT OF INVESTMENTS June 30, 2015


	Shares		Value
Common Stocks—98.9%
Consumer Discretionary—14.3%
Auto Components—2.1%
Dana Holding Corp.		3,784,490	$	77,884,804

Hotels, Restaurants & Leisure—3.5%
Brinker International, Inc.		1,079,830		62,252,199
Dunkin’ Brands Group, Inc.		1,152,745		63,400,975
				125,653,174

Household Durables—0.8%
Toll Brothers, Inc.¹		797,529		30,457,633

Media—0.8%
IMAX Corp.¹		678,843		27,337,008

Specialty Retail—6.2%
Foot Locker, Inc.		770,690		51,643,937
O’Reilly Automotive, Inc.¹		223,690		50,549,466
Ross Stores, Inc.		1,166,730		56,714,745
Sally Beauty Holdings, Inc.¹		2,056,200		64,934,796
				223,842,944

Textiles, Apparel & Luxury Goods—0.9%
PVH Corp.		297,081		34,223,731

Consumer Staples—3.8%
Beverages—0.8%
Coca-Cola Enterprises, Inc.		653,300		28,379,352

Food & Staples Retailing—0.7%
Rite Aid Corp.¹		2,740,531		22,883,434

Food Products—1.5%
Flowers Foods, Inc.		2,606,951		55,137,014

Personal Products—0.8%
Nu Skin Enterprises, Inc., Cl. A		622,110		29,320,044

Energy—4.8%
Oil, Gas & Consumable Fuels—4.8%
Antero Midstream Partners LP²		986,151		28,243,365
Cameco Corp.		1,916,160		27,362,765


	Shares		Value
Oil, Gas & Consumable Fuels (Continued)
Magellan Midstream Partners LP²		251,060	$	18,422,783
Noble Energy, Inc.		1,309,081		55,871,577
Western Refining, Inc.		1,045,460		45,602,965
				175,503,455

Financials—21.7%
Commercial Banks—2.7%
Comerica, Inc.		1,167,960		59,939,707
Huntington Bancshares, Inc.		3,427,673		38,766,982
				98,706,689

Consumer Finance—3.7%
Discover Financial Services		1,313,370		75,676,380
Navient Corp.		3,208,120		58,419,865
				134,096,245

Diversified Financial Services—2.3%
CME Group, Inc., Cl. A		909,024		84,593,773

Insurance—4.5%
Aflac, Inc.		530,620		33,004,564
FNF Group		2,448,060		90,553,739
XL Group plc, Cl. A		1,015,360		37,771,392
				161,329,695

Real Estate Investment Trusts (REITs)—8.5%
American Capital Agency Corp.		3,890,230		71,463,525
Digital Realty Trust, Inc.		853,353		56,901,578
Lamar Advertising Co., Cl. A		1,012,790		58,215,170
Mid-America Apartment Communities, Inc.		1,046,199		76,173,749
Outfront Media, Inc.		1,757,117		44,349,633
				307,103,655

12 OPPENHEIMER MAIN STREET MID CAP FUND


	Shares		Value
Health Care—16.4%
Biotechnology—1.2%
BioMarin Pharmaceutical, Inc.¹		235,980	$	32,277,344
Celldex Therapeutics, Inc.¹		412,450		10,401,989
				42,679,333

Health Care Equipment & Supplies—3.6%
Align Technology, Inc.¹		485,920		30,472,043
Boston Scientific Corp.¹		4,175,010		73,897,677
DexCom, Inc.¹		342,781		27,415,625
				131,785,345

Health Care Providers & Services—9.8%
Centene Corp.¹		1,133,344		91,120,857
Envision Healthcare Holdings, Inc.¹		2,022,670		79,855,012
HealthSouth Corp.		1,386,434		63,859,150
Omnicare, Inc.		202,483		19,084,023
Universal Health Services, Inc., Cl. B		710,039		100,896,542
				354,815,584

Pharmaceuticals—1.8%
Akorn, Inc.¹		459,220		20,049,545
Mallinckrodt plc¹		391,770		46,119,165
				66,168,710

Industrials—13.5%
Aerospace & Defense—2.4%
L-3 Communications Holdings, Inc.		770,170		87,321,874

Airlines—1.9%
Spirit Airlines, Inc.¹		1,107,100		68,750,910

Commercial Services & Supplies—3.5%
Tyco International plc		2,024,337		77,896,488
Waste Connections, Inc.		1,073,178		50,568,147
				128,464,635


	Shares		Value
Electrical Equipment—0.5%
Generac Holdings, Inc.¹		465,480	$	18,502,830

Machinery—1.3%
Joy Global, Inc.		1,276,069		46,193,698

Professional Services—1.7%
On Assignment, Inc.¹		55,029		2,161,539
Robert Half International, Inc.		1,084,610		60,195,855
				62,357,394

Road & Rail—1.7%
Genesee & Wyoming, Inc., Cl. A¹		803,640		61,221,295

Trading Companies & Distributors—0.5%
NOW, Inc.¹		834,760		16,620,072

Information Technology—12.2%
Internet Software & Services—0.8%
Pandora Media, Inc.¹		1,817,560		28,244,883

IT Services—1.5%
Amdocs Ltd.		583,805		31,869,915
Xerox Corp.		2,164,110		23,026,130
				54,896,045

Semiconductors & Semiconductor Equipment— 3.7%
Applied Materials, Inc.		3,202,170		61,545,708
Cavium, Inc.¹		580,443		39,940,283
Skyworks Solutions, Inc.		312,474		32,528,543
				134,014,534

Software—5.6%
Fortinet, Inc.¹		1,340,711		55,411,586
Guidewire Software, Inc.¹		1,157,185		61,249,802
PTC, Inc.¹		677,754		27,801,469
ServiceNow, Inc.¹		516,840		38,406,380
Splunk, Inc.¹		327,910		22,829,094
				205,698,331

Technology Hardware, Storage & Peripherals— 0.6%
Western Digital Corp.		266,352		20,887,324

13 OPPENHEIMER MAIN STREET MID CAP FUND

STATEMENT OF INVESTMENTS Unaudited / Continued


	Shares		Value
Materials—7.9%
Chemicals—3.5%
Eastman Chemical Co.		920,740	$	75,334,947
International Flavors & Fragrances, Inc.		460,440		50,321,488
				125,656,435

Containers & Packaging—0.8%
Packaging Corp. of America		449,762		28,105,627

Metals & Mining—3.6%
Alcoa, Inc.		6,882,280		76,737,422

Franco-Nevada Corp.		1,160,200		55,283,530
				132,020,952

Utilities—4.3%
Electric Utilities—2.2%
ALLETE, Inc.		884,160		41,016,182
Exelon Corp.		1,210,372		38,029,888
				79,046,070


	Shares		Value
Multi-Utilities—1.5%
Consolidated Edison, Inc.		487,800	$	28,233,864
PG&E Corp.		560,050		27,498,455
				55,732,319

Water Utilities—0.6%
Aqua America, Inc.		904,832		22,159,336
Total Common Stocks (Cost $3,067,653,609)				3,587,796,186

Investment Company—3.3%
Oppenheimer Institutional Money Market Fund, Cl. E, 0.15%^3,4(Cost $119,672,700)		119,672,700		119,672,700
Total Investments, at Value (Cost $3,187,326,309)		102.2%		3,707,468,886
Net Other Assets (Liabilities)		(2.2)		(79,358,104	)
Net Assets		100.0%	$	3,628,110,782

Footnotes to Statement of Investments

1. Non-income producing security.

2. Security is a Master Limited Partnership.

3. Is or was an affiliate, as defined in the Investment Company Act of 1940, as amended, at or during the period ended June 30, 2015, 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 30, 2014		Gross Additions		Gross Reductions		Shares June 30, 2015
Oppenheimer Institutional Money Market Fund, Cl. E		135,970,960		1,591,542,678		1,607,840,938		119,672,700

					Value		Income
Oppenheimer Institutional Money Market Fund, Cl. E					$	119,672,700	$	113,598

4. Rate shown is the 7-day yield as of June 30, 2015.

See accompanying Notes to Financial Statements.

14 OPPENHEIMER MAIN STREET MID CAP FUND

STATEMENT OF ASSETS AND LIABILITIES June 30, 2015



Assets
Investments, at value—see accompanying statement of investments:
Unaffiliated companies (cost $3,067,653,609)	$	3,587,796,186
Affiliated companies (cost $119,672,700)		119,672,700

		3,707,468,886

Cash		4,999,996

Receivables and other assets:
Investments sold		7,802,383
Dividends		3,428,125
Shares of beneficial interest sold		1,393,522
Other		184,937

Total assets		3,725,277,849


Liabilities
Payables and other liabilities:
Investments purchased		92,732,432
Shares of beneficial interest redeemed		3,685,751
Distribution and service plan fees		515,361
Trustees’ compensation		158,879
Shareholder communications		27,959
Other		46,685

Total liabilities		97,167,067


Net Assets	$	3,628,110,782



Composition of Net Assets
Par value of shares of beneficial interest	$	120,445

Additional paid-in capital		2,755,677,385

Accumulated net investment income		12,561,467

Accumulated net realized gain on investments		339,608,908

Net unrealized appreciation on investments		520,142,577

Net Assets	$	3,628,110,782

15 OPPENHEIMER MAIN STREET 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 $1,806,591,857 and 59,912,360 shares of beneficial interest outstanding)	$	30.15
Maximum offering price per share (net asset value plus sales charge of 5.75% of offering price)	$	31.99


Class B Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $32,757,235 and 1,255,376 shares of beneficial interest outstanding)	$	26.09


Class C Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $386,109,121 and 14,684,847 shares of beneficial interest outstanding)	$	26.29


Class I Shares:
Net asset value, redemption price and offering price per share (based on net assets of $491,235,359 and 15,376,255 shares of beneficial interest outstanding)	$	31.95


Class R Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $222,755,134 and 7,690,271 shares of beneficial interest outstanding)	$	28.97


Class Y Shares:
Net asset value, redemption price and offering price per share (based on net assets of $688,662,076 and 21,525,950 shares of beneficial interest outstanding)	$	31.99

See accompanying Notes to Financial Statements.

16 OPPENHEIMER MAIN STREET MID CAP FUND

STATEMENT OF OPERATIONS For the Year Ended June 30, 2015



Investment Income
Dividends:
Unaffiliated companies (net of foreign withholding taxes of $58,159)	$	57,358,812
Affiliated companies		113,598

Interest		1,061

Total investment income		57,473,471


Expenses
Management fees		23,149,194

Distribution and service plan fees:
Class A		4,603,610
Class B		412,033
Class C		3,910,061
Class R¹		1,134,563

Transfer and shareholder servicing agent fees:
Class A		4,114,642
Class B		90,985
Class C		861,555
Class I		158,537
Class R¹		500,064
Class Y		1,450,180

Shareholder communications:
Class A		44,702
Class B		3,401
Class C		9,548
Class I		73
Class R¹		3,757
Class Y		4,585

Trustees’ compensation		107,194

Custodian fees and expenses		18,274

Other		155,603

Total expenses		40,732,561
Less reduction to custodian expenses		(1,795)
Less waivers and reimbursements of expenses		(108,414)

Net expenses		40,622,352

Net Investment Income		16,851,119

Realized and Unrealized Gain (Loss)
Net realized gain on investments from unaffiliated companies		520,517,248

Net change in unrealized appreciation/depreciation on investments		(338,822,185)


Net Increase in Net Assets Resulting from Operations	$	198,546,182

1. Effective July 1, 2014, Class N shares were renamed Class R. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

17 OPPENHEIMER MAIN STREET MID CAP FUND

STATEMENTS OF CHANGES IN NET ASSETS


	Year Ended June 30, 2015		Year Ended June 30, 2014

Operations
Net investment income	$	16,851,119	$	21,375,999

Net realized gain		520,517,248		672,136,333

Net change in unrealized appreciation/depreciation		(338,822,185)		201,805,806

Net increase in net assets resulting from operations		198,546,182		895,318,138

Dividends and/or Distributions to Shareholders
Dividends from net investment income:
Class A		(10,359,751)		(892,711)
Class B		—		—
Class C		(2,188)		—
Class I		(4,253,234)		(2,812,218)
Class R¹		(804,465)		—
Class Y		(5,396,050)		(1,523,584)

		(20,815,688)		(5,228,513)

Distributions from net realized gain:
Class A		(250,861,303)		—
Class B		(6,415,172)		—
Class C		(59,110,058)		—
Class I		(57,437,945)		—
Class R¹		(31,786,566)		—
Class Y		(87,269,686)		—

		(492,880,730)		—

Beneficial Interest Transactions
Net increase (decrease) in net assets resulting from beneficial interest transactions:
Class A		(32,102,092)		(164,574,172)
Class B		(14,251,431)		(19,537,242)
Class C		29,722,649		(23,429,544)
Class I		(109,775,022)		154,741,445
Class R¹		7,818,963		(44,034,688)
Class Y		140,649,915		(357,296,104)

		22,062,982		(454,130,305)

Net Assets
Total increase (decrease)		(293,087,254)		435,959,320

Beginning of period		3,921,198,036		3,485,238,716

End of period (including accumulated net investment income of $12,561,467 and $19,393,196, respectively)	$	3,628,110,782	$	3,921,198,036

1. Effective July 1, 2014, Class N shares were renamed Class R. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

18 OPPENHEIMER MAIN STREET MID CAP FUND

FINANCIAL HIGHLIGHTS


Class A	Year Ended June 30, 2015		Year Ended June 30, 2014		Year Ended June 28, 2013¹		Year Ended June 29, 2012¹		Year Ended June 30, 2011

Per Share Operating Data
Net asset value, beginning of period	$	33.30	$	26.17	$	21.75	$	21.99	$	16.33

Income (loss) from investment operations:
Net investment income²		0.14		0.17		0.15		0.04		0.05
Net realized and unrealized gain (loss)		1.47		6.97		4.45		(0.23)		5.61

Total from investment operations		1.61		7.14		4.60		(0.19)		5.66

Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.19)		(0.01)		(0.18)		(0.05)		0.00
Distributions from net realized gain		(4.57)		0.00		0.00		0.00		0.00

Total dividends and/or distributions to shareholders		(4.76)		(0.01)		(0.18)		(0.05)		0.00

Net asset value, end of period	$	30.15	$	33.30	$	26.17	$	21.75	$	21.99


Total Return, at Net Asset Value³		5.58%		27.31%		21.30%		(0 .85)%		34.66%


Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	1,806,592	$	1,999,887	$	1,716,475	$	1,662,531	$	2,026,656

Average net assets (in thousands)	$	1,870,139	$	1,876,128	$	1,708,977	$	1,696,301	$	2,016,616

Ratios to average net assets:⁴
Net investment income		0.46%		0.57%		0.62%		0.20%		0.28%
Total expenses⁵		1.10%		1.12%		1.19%		1.24%		1.25%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		1.10%		1.12%		1.19%		1.24%		1.24%

Portfolio turnover rate		82 %		63 %		101 %		81 %		86 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective reporting periods.

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. The returns do not include adjustments in accordance with generally accepted accounting principles required at the period end for financial reporting purposes.

4. Annualized for periods less than one full year.

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


Year Ended June 30, 2015			1.10%
Year Ended June 30, 2014			1.12%
Year Ended June 28, 2013			1.19%
Year Ended June 29, 2012			1.24%
Year Ended June 30, 2011			1.25%

See accompanying Notes to Financial Statements.

19 OPPENHEIMER MAIN STREET MID CAP FUND

FINANCIAL HIGHLIGHTS Continued


Class B	Year Ended June 30, 2015		Year Ended June 30, 2014		Year Ended June 28, 2013¹		Year Ended June 29, 2012¹		Year Ended June 30, 2011

Per Share Operating Data
Net asset value, beginning of period	$	29.47	$	23.33	$	19.40	$	19.72	$	14.77

Income (loss) from investment operations:
Net investment loss²		(0.08)		(0.06)		(0.05)		(0.11)		(0.09)
Net realized and unrealized gain (loss)		1.27		6.20		3.98		(0.21)		5.04

Total from investment operations		1.19		6.14		3.93		(0.32)		4.95

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		(4.57)		0.00		0.00		0.00		0.00

Total dividends and/or distributions to shareholders		(4.57)		0.00		0.00		0.00		0.00

Net asset value, end of period	$	26.09	$	29.47	$	23.33	$	19.40	$	19.72


Total Return, at Net Asset Value³		4.78%		26.32%		20.26%		(1.62)%		33.51%


Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	32,757	$	51,449	$	57,999	$	69,088	$	102,861

Average net assets (in thousands)	$	41,300	$	55,373	$	62,574	$	76,237	$	107,948

Ratios to average net assets:⁴
Net investment loss		(0.29)%		(0.24)%		(0.22)%		(0.63)%		(0.51)%
Total expenses⁵		1.86%		1.98%		2.26%		2.33%		2.29%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		1.86%		1.91%		2.06%		2.06%		2.04%

Portfolio turnover rate		82 %		63 %		101 %		81 %		86 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective reporting periods.

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

4. Annualized for periods less than one full year.

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


Year Ended June 30, 2015			1.86%
Year Ended June 30, 2014			1.98%
Year Ended June 28, 2013			2.26%
Year Ended June 29, 2012			2.33%
Year Ended June 30, 2011			2.29%

See accompanying Notes to Financial Statements.

20 OPPENHEIMER MAIN STREET MID CAP FUND


Class C	Year Ended June 30, 2015		Year Ended June 30, 2014		Year Ended June 28, 2013¹		Year Ended June 29, 2012¹		Year Ended June 30, 2011

Per Share Operating Data
Net asset value, beginning of period	$	29.66	$	23.47	$	19.53	$	19.84	$	14.85

Income (loss) from investment operations:
Net investment loss²		(0.08)		(0.05)		(0.03)		(0.10)		(0.08)
Net realized and unrealized gain (loss)		1.28		6.24		4.01		(0.21)		5.07

Total from investment operations		1.20		6.19		3.98		(0.31)		4.99

Dividends and/or distributions to shareholders:
Dividends from net investment income		0.00		0.00		(0.04)		0.00		0.00
Distributions from net realized gain		(4.57)		0.00		0.00		0.00		0.00

Total dividends and/or distributions to shareholders		(4.57)		0.00		(0.04)		0.00		0.00

Net asset value, end of period	$	26.29	$	29.66	$	23.47	$	19.53	$	19.84



Total Return, at Net Asset Value³		4.78%		26.38%		20.39%		(1.56)%		33.60%


Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	386,109	$	397,240	$	334,870	$	320,566	$	384,059

Average net assets (in thousands)	$	391,675	$	370,920	$	326,360	$	327,119	$	369,499

Ratios to average net assets:⁴
Net investment loss		(0.29)%		(0.18)%		(0.13)%		(0.56)%		(0.45)%
Total expenses⁵		1.85%		1.86%		1.94%		2.00%		1.99%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		1.85%		1.86%		1.94%		2.00%		1.97%

Portfolio turnover rate		82 %		63 %		101 %		81 %		86 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective reporting periods.

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

4. Annualized for periods less than one full year.

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


Year Ended June 30, 2015			1.85%
Year Ended June 30, 2014			1.86%
Year Ended June 28, 2013			1.94%
Year Ended June 29, 2012			2.00%
Year Ended June 30, 2011			1.99%

See accompanying Notes to Financial Statements.

21 OPPENHEIMER MAIN STREET MID CAP FUND

FINANCIAL HIGHLIGHTS Continued


	Year Ended		Year Ended Period Ended
Class I	June 30, 2015		June 30, 2014		June 28, 2013^1,2

Per Share Operating Data
Net asset value, beginning of period	$	35.00	$	27.52	$	23.31

Income (loss) from investment operations:
Net investment income³		0.28		0.35		0.20
Net realized and unrealized gain		1.58		7.29		4.33

Total from investment operations		1.86		7.64		4.53

Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.34)		(0.16)		(0.32)
Distributions from net realized gain		(4.57)		0.00		0.00

Total dividends and/or distributions to shareholders		(4.91)		(0.16)		(0.32)

Net asset value, end of period	$	31.95	$	35.00	$	27.52



Total Return, at Net Asset Value⁴		6.08%		27.83%		19.65%


Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	491,236	$	633,358	$	362,310

Average net assets (in thousands)	$	527,809	$	506,714	$	68,428

Ratios to average net assets:⁵
Net investment income		0.84%		1.11%		1.08%
Total expenses⁶		0.66%		0.66%		0.66%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.66%		0.66%		0.66%

Portfolio turnover rate		82 %		63 %		101 %

1. June 28, 2013 represents the last business day of the Fund’s reporting period.

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. The returns do not include adjustments in accordance with generally accepted accounting principles required at the period end for financial reporting purposes.

5. Annualized for periods less than one full year.

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


Year Ended June 30, 2015			0.66%
Year Ended June 30, 2014			0.66%
Period Ended June 28, 2013			0.66%

See accompanying Notes to Financial Statements.

22 OPPENHEIMER MAIN STREET MID CAP FUND


Class R	Year Ended June 30, 2015		Year Ended June 30, 2014		Year Ended June 28, 2013¹		Year Ended June 29, 2012¹		Year Ended June 30, 2011

Per Share Operating Data
Net asset value, beginning of period	$	32.18	$	25.35	$	21.07	$	21.30	$	15.86

Income (loss) from investment operations:
Net investment income (loss)²		0.06		0.08		0.08		(0.01)		0.01
Net realized and unrealized gain (loss)		1.42		6.75		4.31		(0.22)		5.43

Total from investment operations		1.48		6.83		4.39		(0.23)		5.44

Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.12)		0.00		(0.11)		0.00		0.00
Distributions from net realized gain		(4.57)		0.00		0.00		0.00		0.00

Total dividends and/or distributions to shareholders		(4.69)		0.00		(0.11)		0.00		0.00


Net asset value, end of period	$	28.97	$	32.18	$	25.35	$	21.07	$	21.30



Total Return, at Net Asset Value³		5.33%		26.94%		20.94%		(1.08)%		34.30%


Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	222,755	$	236,139	$	224,448	$	227,261	$	273,682

Average net assets (in thousands)	$	227,331	$	234,597	$	221,263	$	232,102	$	269,808

Ratios to average net assets:⁴
Net investment income (loss)		0.21%		0.28%		0.33%		(0.07)%		0.03%
Total expenses⁵		1.35%		1.39%		1.53%		1.57%		1.60%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		1.35%		1.39%		1.49%		1.51%		1.49%

Portfolio turnover rate		82 %		63 %		101 %		81 %		86 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective reporting periods.

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

4. Annualized for periods less than one full year.

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


Year Ended June 30, 2015			1.35%
Year Ended June 30, 2014			1.39%
Year Ended June 28, 2013			1.53%
Year Ended June 29, 2012			1.57%
Year Ended June 30, 2011			1.60%

See accompanying Notes to Financial Statements.

23 OPPENHEIMER MAIN STREET MID CAP FUND

FINANCIAL HIGHLIGHTS Continued


Class Y	Year Ended June 30, 2015		Year Ended June 30, 2014		Year Ended June 28, 2013¹		Year Ended June 29, 2012¹		Year Ended June 30, 2011

Per Share Operating Data
Net asset value, beginning of period	$	35.05	$	27.53	$	22.88	$	23.12	$	17.17

Income (loss) from investment operations:
Net investment income²		0.24		0.24		0.25		0.13		0.14
Net realized and unrealized gain (loss)		1.55		7.36		4.68		(0.24)		5.89

Total from investment operations		1.79		7.60		4.93		(0.11)		6.03

Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.28)		(0.08)		(0.28)		(0.13)		(0.08)
Distributions from net realized gain		(4.57)		0.00		0.00		0.00		0.00

Total dividends and/or distributions to shareholders		(4.85)		(0.08)		(0.28)		(0.13)		(0.08)

Net asset value, end of period	$	31.99	$	35.05	$	27.53	$	22.88	$	23.12



Total Return, at Net Asset Value³		5.86%		27.63%		21.74%		(0.40)%		35.14%


Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	688,662	$	603,125	$	789,137	$	908,339	$	1,059,058

Average net assets (in thousands)	$	659,360	$	686,659	$	977,581	$	904,802	$	992,951

Ratios to average net assets:⁴
Net investment income		0.72%		0.76%		1.00%		0.60%		0.69%
Total expenses⁵		0.85%		0.84%		0.81%		0.85%		0.83%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.85%		0.84%		0.81%		0.85%		0.83%

Portfolio turnover rate		82 %		63 %		101 %		81 %		86 %

1. June 28, 2013 and June 29, 2012 represent the last business days of the Fund’s respective reporting periods.

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

4. Annualized for periods less than one full year.

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


Year Ended June 30, 2015			0.85%
Year Ended June 30, 2014			0.84%
Year Ended June 28, 2013			0.81%
Year Ended June 29, 2012			0.85%
Year Ended June 30, 2011			0.83%

See accompanying Notes to Financial Statements.

24 OPPENHEIMER MAIN STREET MID CAP FUND

NOTES TO FINANCIAL STATEMENTS June 30, 2015

1. Organization

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

The Fund offers Class A, Class C, Class I, Class R 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. As of July 1, 2014, Class N shares were renamed Class R shares. Class N shares subject to a contingent deferred sales charge (“CDSC”) on July 1, 2014, will continue to be subject to a CDSC after the shares are renamed. Purchases of Class R shares occurring on or after July 1, 2014, will not be subject to a CDSC upon redemption. 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 R 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 R shares are sold only through retirement plans. Retirement plans that offer Class R 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 R 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 followed in the Fund’s preparation of financial statements in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”).

2. Significant Accounting Policies

Security Valuation. All investments in securities are recorded at their estimated fair value, as described in Note 3.

Reporting Period End Date. The last day of the Fund’s reporting period is the last day the New York Stock Exchange was open for trading during the period. The Fund’s financial statements have been presented through that date to maintain consistency with the Fund’s net asset value calculations used for shareholder transactions.

25 OPPENHEIMER MAIN STREET MID CAP FUND

NOTES TO FINANCIAL STATEMENTS Continued

2. Significant Accounting Policies (Continued)

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.

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.

Return of Capital Estimates. Distributions received from the Fund’s investments in MLPs generally are comprised of income and return of capital. The Fund records investment income and return of capital based on estimates made at the time such distributions are received. Such estimates are based on historical information available from each MLP and other industry sources. These estimates may subsequently be revised based on information received from MLPs after their tax reporting periods are concluded.

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

26 OPPENHEIMER MAIN STREET MID CAP FUND

2. Significant Accounting Policies (Continued)

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.

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 remains 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.

Net Unrealized

Appreciation

Based on cost of

Securities and

Undistributed

Accumulated

Other Investments

Net Investment

Long-Term

Loss

for Federal Income

Income

Gain

Carryforward^1,2

Tax Purposes

$35,935,950

$323,741,615

$—

$512,794,267

1. During the fiscal year ended June 30, 2015, the Fund did not utilize any capital loss carryforward.

2. During the fiscal year ended June 30, 2014, the Fund utilized $262,355,498 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 from net investment income or net realized gains are determined in accordance with federal income tax requirements, which may differ from the character of net investment income or net realized gains presented in those financial statements in accordance with GAAP. 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, 2015. Net assets of the Fund were unaffected by the reclassifications.


	Reduction		Reduction
	to Accumulated		to Accumulated Net
Increase	Net Investment		Realized Gain
to Paid-in Capital	Income		on Investments³
$43,004,928		$2,867,160		$40,137,768

3. $50,153,902, including $46,737,959 of long-term capital gain, was distributed in connection with Fund share redemptions.

27 OPPENHEIMER MAIN STREET MID CAP FUND

NOTES TO FINANCIAL STATEMENTS Continued

2. Significant Accounting Policies (Continued)

The tax character of distributions paid during the years ended June 30, 2015 and June 30, 2014 was as follows:


	Year Ended		Year Ended
	June 30, 2015		June 30, 2014

Distributions paid from:
Ordinary income	$	61,927,980	$	5,228,520
Long-term capital gain		451,768,438		—

Total	$	513,696,418	$	5,228,520

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 30, 2015 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	$	3,194,674,619

Gross unrealized appreciation	$	671,047,410
Gross unrealized depreciation		(158,253,143)

Net unrealized appreciation	$	512,794,267

Use of Estimates. 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.

3. 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.

28 OPPENHEIMER MAIN STREET MID CAP FUND

3. Securities Valuation (Continued)

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 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.

29 OPPENHEIMER MAIN STREET MID CAP FUND

NOTES TO FINANCIAL STATEMENTS Continued

3. Securities Valuation (Continued)

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 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.)

30 OPPENHEIMER MAIN STREET MID CAP FUND

3. Securities Valuation (Continued)

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 30, 2015 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	$	519,399,294	$	—	$	—	$	519,399,294
Consumer Staples		135,719,844		—		—		135,719,844
Energy		175,503,455		—		—		175,503,455
Financials		785,830,057		—		—		785,830,057
Health Care		595,448,972		—		—		595,448,972
Industrials		489,432,708		—		—		489,432,708
Information Technology		443,741,117		—		—		443,741,117
Materials		285,783,014		—		—		285,783,014
Utilities		156,937,725		—		—		156,937,725
Investment Company		119,672,700		—		—		119,672,700

Total Assets	$	3,707,468,886	$	—	$	—	$	3,707,468,886

Forward currency exchange contracts and futures contracts, if any, are reported at their unrealized appreciation/depreciation at measurement date, which represents the change in the contract’s value from trade date. All additional assets and liabilities included in the above table are reported at their market value at measurement date.

4. Investments and Risks

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 or for defensive purposes. IMMF is a registered open-end management investment company, regulated as a money market fund under the 1940 Act. 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 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.

31 OPPENHEIMER MAIN STREET MID CAP FUND

NOTES TO FINANCIAL STATEMENTS Continued

4. Investments and Risks (Continued)

Master Limited Partnerships (“MLPs”). MLPs issue common units that represent an equity ownership interest in a partnership and provide limited voting rights. MLP common units are registered with the Securities and Exchange Commission (“SEC”), and are freely tradable on securities exchanges such as the NYSE and the NASDAQ Stock Market (“NASDAQ”), or in the over-the-counter (“OTC”) market. An MLP consists of one or more general partners, who conduct the business, and one or more limited partners, who contribute capital. MLP common unit holders have a limited role in the partnership’s operations and management. The Fund, as a limited partner, normally would not be liable for the debts of the MLP beyond the amounts the Fund has contributed, but would not be shielded to the same extent that a shareholder of a corporation would be. In certain circumstances creditors of an MLP would have the right to seek return of capital distributed to a limited partner. This right of an MLP’s creditors would continue after the Fund sold its investment in the MLP.

Equity Security Risk. Stocks and other equity securities fluctuate in price. The value of the Fund’s portfolio may be affected by changes in the equity markets generally. Equity markets may experience significant short-term volatility and may fall sharply at times. Different markets may behave differently from each other and U.S. equity markets may move in the opposite direction from one or more foreign stock markets. Adverse events in any part of the equity or fixed-income markets may have unexpected negative effects on other market segments.

The prices of individual equity securities generally do not all move in the same direction at the same time and a variety of factors can affect the price of a particular company’s securities. These factors may include, but are not limited to, poor earnings reports, a loss of customers, litigation against the company, general unfavorable performance of the company’s sector or industry, or changes in government regulations affecting the company or its industry.

5. 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 30, 2015				Year Ended June 30, 2014
	Shares		Amount		Shares		Amount

Class A
Sold		8,383,895	$	261,906,812		8,053,385	$	239,302,251
Dividends and/or distributions reinvested		8,630,354		247,345,952		28,823		846,538
Redeemed		(17,160,930)		(541,354,856)		(13,607,293)		(404,722,961)

Net decrease		(146,681)	$	(32,102,092)		(5,525,085)	$	(164,574,172)

32 OPPENHEIMER MAIN STREET MID CAP FUND

5. Shares of Beneficial Interest (Continued)


	Year Ended June 30, 2015				Year Ended June 30, 2014
	Shares		Amount		Shares		Amount

Class B
Sold		66,983	$	1,844,415		83,089	$	2,179,662
Dividends and/or distributions reinvested		254,424		6,337,698		—		—
Redeemed		(811,961)		(22,433,544)		(822,822)		(21,716,904)

Net decrease		(490,554)	$	(14,251,431)		(739,733)	$	(19,537,242)



Class C
Sold		1,785,730	$	48,727,078		1,732,140	$	46,203,993
Dividends and/or distributions reinvested		2,183,479		54,805,316		—		—
Redeemed		(2,678,866)		(73,809,745)		(2,603,567)		(69,633,537)

Net increase (decrease)		1,290,343	$	29,722,649		(871,427)	$	(23,429,544)



Class I
Sold		2,905,234	$	93,533,786		7,644,932	$	241,172,541
Dividends and/or distributions reinvested		2,036,498		61,685,537		91,280		2,810,508
Redeemed		(7,659,047)		(264,994,345)		(2,809,756)		(89,241,604)

Net increase (decrease)		(2,717,315)	$	(109,775,022)		4,926,456	$	154,741,445



Class R¹
Sold		2,067,314	$	61,781,446		1,712,426	$	48,896,112
Dividends and/or distributions reinvested		1,106,186		30,497,548		—		—
Redeemed		(2,822,410)		(84,460,031)		(3,228,681)		(92,930,800)

Net increase (decrease)		351,090	$	7,818,963		(1,516,255)	$	(44,034,688)



Class Y
Sold		8,623,565	$	290,431,422		3,728,341	$	115,986,149
Dividends and/or distributions reinvested		2,926,375		88,874,008		46,662		1,440,456
Redeemed		(7,230,786)		(238,655,515)		(15,231,450)		(474,722,709)

Net increase (decrease)		4,319,154	$	140,649,915		(11,456,447)	$	(357,296,104)

1. Effective July 1, 2014, Class N shares were renamed Class R.

6. 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 30, 2015 were as follows:


	Purchases		Sales

Investment securities	$	2,971,733,560	$	3,337,091,634

33 OPPENHEIMER MAIN STREET MID CAP FUND

NOTES TO FINANCIAL STATEMENTS Continued

7. 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

The Fund’s effective management fee for the fiscal year ended June 30, 2015 was 0.62% of average annual net assets before any applicable waivers.

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. OFI Global (the “Transfer Agent”) serves as the transfer and shareholder servicing agent for the Fund. The Fund pays the Transfer Agent a fee based on annual net assets. Fees incurred and average net assets for each class with respect to these services are detailed in the Statement of Operations and Financial Highlights, respectively.

Sub-Transfer Agent Fees. 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.

Trustees’ Compensation. The Fund’s Board of Trustees (“Board”) 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.

34 OPPENHEIMER MAIN STREET MID CAP FUND

7. Fees and Other Transactions with Affiliates (Continued)

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.

Service Plan for Class A Shares. The Fund has adopted a Service Plan (the “Plan”) for Class A shares pursuant to Rule 12b-1 under the 1940 Act. 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 R Shares. The Fund has adopted Distribution and Service Plans (the “Plans”) for Class B, Class C and Class R shares pursuant to Rule 12b-1 under the 1940 Act to compensate the Distributor for distributing those share classes, maintaining accounts and providing shareholder services. 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 R shares daily net assets. The Fund also pays a service fee under the Plans at an annual rate of 0.25% of daily net assets. The Plans continue in effect from year to year only if the Fund’s Board of Trustees vote annually to approve its continuance at an in person meeting called for that purpose. Fees incurred by the Fund under the Plans are detailed in the Statement of Operations.

Sales Charges. Front-end sales charges and CDSC do not represent expenses of the Fund. They are deducted from the proceeds of sales of Fund 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 R Contingent Deferred Sales Charges Retained by Distributor

June 30, 2015		$353,184		$331		$29,512		$12,787		$2,341

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 30, 2015, the Manager waived fees and/or reimbursed the Fund $108,414 for IMMF management fees.

35 OPPENHEIMER MAIN STREET MID CAP FUND

NOTES TO FINANCIAL STATEMENTS Continued

7. Fees and Other Transactions with Affiliates (Continued)

Waivers and/or reimbursements may be modified or terminated as set forth according to the terms in the prospectus.

8. Pending Litigation

In 2009, several lawsuits were filed as putative class actions and later consolidated before the U.S. District Court for the District of Colorado in connection with the investment performance of Oppenheimer Rochester California Municipal Fund (the “California Fund Suit”), a fund advised by OppenheimerFunds, Inc. (“OFI”), and distributed by its subsidiary OppenheimerFunds Distributor, Inc. ( “OFDI”). The plaintiffs asserted claims against OFI, OFDI and certain present and former trustees and officers of the Fund under the federal securities laws, alleging, among other things, that the disclosure documents of the Fund contained misrepresentations and omissions and the investment policies of the Fund were not followed. Plaintiffs in the California Fund Suit filed an amended complaint and defendants filed a motion to dismiss. In 2011, the court issued an order which granted in part and denied in part the defendants’ motion to dismiss. In 2012, plaintiffs filed a motion, which defendants opposed, to certify a class and appoint class representatives and class counsel. In March 2015, the court granted plaintiffs’ motion for class certification. In May 2015, the U.S. Court of Appeals for the Tenth Circuit vacated the class certification order and remanded the matter to the district court for further proceedings. In July 2015, the district court held an evidentiary hearing on plaintiffs’ motion for class certification. OFI and OFDI believe the California Fund Suit is without merit; that it is premature to render any opinion as to the likelihood of an outcome unfavorable to them in the California Fund Suit; and that no estimate can yet be made as to the amount or range of any potential loss.

36 OPPENHEIMER MAIN STREET MID CAP FUND

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

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

We have audited the accompanying statement of assets and liabilities of Oppenheimer Main Street Mid Cap Fund, including the statement of investments, as of June 30, 2015, 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 30, 2015, by correspondence with the custodian, transfer agent 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 Mid Cap Fund as of June 30, 2015, 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 12, 2015

37 OPPENHEIMER MAIN STREET MID CAP FUND

FEDERAL INCOME TAX INFORMATION Unaudited

In early 2015, if applicable, shareholders of record received information regarding all dividends and distributions paid to them by the Fund during calendar year 2014.

Capital gain distributions of $4.19085 per share were paid to Class A, Class B, Class C, Class I, Class R and Class Y shareholders, respectively, on December 10, 2014. Whether received in stock or in cash, the capital gain distribution should be treated by shareholders as a gain from the sale of the capital assets held for more than one year (long-term capital gains).

Dividends, if any, paid by the Fund during the fiscal year ended June 30, 2015 which are not designated as capital gain distributions should be multiplied by the maximum amount allowable but not less than 68.72% 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 30, 2015 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 $46,044,986 of the Fund’s fiscal year taxable income may be eligible for the lower individual income tax rates. In early 2015, 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 30, 2015, the maximum amount allowable but not less than $35,091 of the ordinary distributions to be paid by the Fund qualifies as an interest related dividend and the maximum amount allowable but not less than $51,965,975 of the short-term capital gain distribution to be paid by the Fund qualifies as a short-term capital gain 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.

38 OPPENHEIMER MAIN STREET MID CAP FUND

PORTFOLIO PROXY VOTING POLICIES AND PROCEDURES; UPDATES TO STATEMENT 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 www.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.

39 OPPENHEIMER MAIN STREET MID CAP FUND

TRUSTEES AND OFFICERS Unaudited


Name, Position(s) Held with the Fund, Length of Service, Year of Birth		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 38 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.

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 38 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 38 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.

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);

40 OPPENHEIMER MAIN STREET MID CAP FUND


Beverly L. Hamilton, Continued		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 38 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		Board Chair (2008-Present) and Director (2004-Present), United Educators (insurance company); Trustee (since 2000) and Chair (since 2010), Newberry Library (independent research library); Trustee, Mather LifeWays (senior living organization) (since 2001); 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 (investment adviser) (and its predecessor firms); 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, BoardSource (non-profit organization) (2006-2009) and Chicago City Day School (K-8 School) (1994-2005). Oversees 38 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 38 portfolios in the OppenheimerFunds complex. Mr. Malone has served on the Boards of certain Oppenheimer funds since 2002, during which time he has become

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TRUSTEES AND OFFICERS Unaudited / Continued


Robert J. Malone, Continued		familiar with the Fund’s (and other Oppenheimer funds’) financial, accounting, regulatory and investment matters and has contributed to the Boards’ deliberations.

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 Funds (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 42 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 (professional services firm) (held various positions 1975-1990); 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 (professional organization) since inception. Oversees 38 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 38 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.

42 OPPENHEIMER MAIN STREET MID CAP FUND


INTERESTED TRUSTEE AND OFFICER		Mr. Steinmetz is an “Interested Trustee” because he is affiliated with the Manager and the Sub-Adviser by virtue of his positions as Chairman of the Sub-Adviser and officer and director of the Manager. Both as a Trustee and as an officer, Mr. Steinmetz serves for an indefinite term, or until his resignation, retirement, death or removal. Mr. Steinmetz’s address is 225 Liberty Street, New York, New York 10281-1008.

Arthur P. Steinmetz, Trustee (since 2015), President and Principal Executive Officer (since 2014) Year of Birth: 1958		Chairman of the Sub-Adviser (since January 2015); CEO and Chairman of the Manager (since July 2014), President of the Manager (since May 2013), a Director of the Manager (since January 2013), Director of the Sub-Adviser (since July 2014), President, Management Director and CEO of Oppenheimer Acquisition Corp. (the Sub-Adviser’s parent holding company) (since July 2014), and President and Director of OFI SteelPath, Inc. (since January 2013). Chief Investment Officer of the OppenheimerFunds advisory entities from (January 2013-December 2013); Executive Vice President of the Manager (January 2013-May 2013); Chief Investment Officer of the Sub-Adviser (October 2010-December 2012); Chief Investment Officer, Fixed-Income, of the Sub-Adviser (April 2009-October 2010); Executive Vice President of the Sub-Adviser (October 2009-December 2012); Director of Fixed Income of the Sub-Adviser (January 2009-April 2009); and a Senior Vice President of the Sub-Adviser (March 1993-September 2009). An officer of 91 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, Sexton and Picciotto, 225 Liberty Street, New York, New York 10281-1008, for Mr. 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). 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.

43 OPPENHEIMER MAIN STREET MID CAP FUND

TRUSTEES AND OFFICERS Unaudited / Continued


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, 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

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Adam Weiner, Continued		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 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 91 portfolios in the OppenheimerFunds complex.

Jennifer Sexton, Vice President and Chief Business Officer (since 2014) Year of Birth: 1969		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 91 portfolios in the OppenheimerFunds complex.

Mary Ann Picciotto, Chief Compliance Officer and Chief Anti-Money Laundering Officer (since 2014) Year of Birth: 1973		Senior Vice President of OppenheimerFunds Distributor, Inc. (since June 2014); Vice President of OppenheimerFunds Distributor, Inc. (April 2006-June 2014); Vice President of the Sub-Adviser (January 1998-March 2006); Assistant Vice President of the Sub-Adviser (October 1991-December 1998). An officer of 91 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

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TRUSTEES AND OFFICERS Unaudited / Continued

Brian W. Wixted,

Continued

Company (since May 2000); Assistant Treasurer of Oppenheimer Acquisition Corporation (March 1999-June 2008). An officer of 91 portfolios in the OppenheimerFunds complex.

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).

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OPPENHEIMER MAIN STREET 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		Ropes & Gray LLP

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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:

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Applications or other forms

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

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

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Your transactions with us, our affiliates or others

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

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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

Copies of confirmations, account statements and other documents reporting activity in your fund accounts are made available to your financial advisor (as designated by you). 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.

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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.

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All transactions, including redemptions, exchanges and purchases, are secured by SSL and 256-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.

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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.

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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., each of its investment adviser subsidiaries, OppenheimerFunds Distributor, Inc. and OFI Global Trust Co. 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 March 2015. 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 this privacy policy, 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).

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55 OPPENHEIMER MAIN STREET MID CAP FUND

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Oppenheimer funds are distributed by OppenheimerFunds Distributor, Inc.

225 Liberty Street, New York, NY 10281-1008

RA0847.001.0615 August 27, 2015

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 $32,200 in fiscal 2015 and $31,500 in fiscal 2014.

(b)	Audit-Related Fees

The principal accountant for the audit of the registrant’s annual financial statements billed no such fees in fiscal 2015 and $1,500 in fiscal 2014.

The principal accountant for the audit of the registrant’s annual financial statements billed $966,117 in fiscal 2015 and $928,146 in fiscal 2014 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, GIPS attestation procedures, 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 2015 and no such fees in fiscal 2014.

The principal accountant for the audit of the registrant’s annual financial statements billed $559,556 in fiscal 2015 and $251,007 in fiscal 2014 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 2015 and no such fees in fiscal 2014.

The principal accountant for the audit of the registrant’s annual financial statements billed no such fees in fiscal 2015 and no such fees in fiscal 2014 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 $1,525,673 in fiscal 2015 and $1,180,653 in fiscal 2014 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 6/30/2015, 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 Mid Cap Fund


By:		/s/ Arthur P. Steinmetz
		Arthur P. Steinmetz
		Principal Executive Officer

Date:		8/10/2015

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/ Arthur P. Steinmetz
		Arthur P. Steinmetz
		Principal Executive Officer

Date:		8/10/2015


By:		/s/ Brian W. Wixted
		Brian W. Wixted
		Principal Financial Officer

Date:		8/10/2015