N-CSRS

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 811-21888

Oppenheimer Institutional Money Market Fund

(Exact name of registrant as specified in charter)

6803 South Tucson Way, Centennial, Colorado 80112-3924

(Address of principal executive offices) (Zip code)

Arthur S. Gabinet

OFI Global Asset Management, Inc.

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

(Name and address of agent for service)

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

Date of fiscal year end: May 31

Date of reporting period: 11/29/2013

Item 1. Reports to Stockholders.

Table of Contents

Fund Performance Discussion	3
Portfolio Allocation and Holdings	5
Fund Expenses	7
Statement of Investments	9
Statement of Assets and Liabilities	15
Statement of Operations	16
Statements of Changes in Net Assets	17
Financial Highlights	18
Notes to Financial Statements	22
Board Approval of the Fund’s Investment Advisory and Sub-Advisory Agreements	31
Special Shareholder Meeting	34
Portfolio Proxy Voting Policies and Procedures; Updates to Statement of Investments	36
Trustees and Officers	37
Privacy Policy Notice	38

2      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Fund Performance Discussion

Although a sustained U.S. economic recovery and expectations of a more moderately accommodative monetary policy drove longer-term interest rates higher over the six-month reporting period, short-term rates remained relatively unchanged. As they have been since December 2008, money market yields stayed anchored by the Federal Reserve’s (the “Fed”) target for the overnight federal funds rate of between 0% and 0.25%.

MARKET OVERVIEW

In the months prior to the start of the reporting period, the U.S. economy rebounded from earlier weakness as the unemployment rate declined, housing markets recovered, and manufacturing activity increased. These economic gains came on the heels of the launch of a new, open-ended round of quantitative easing involving monthly purchases of $85 billion of U.S. government securities. This program from the Fed was designed to add liquidity to the banking system and stimulate higher levels of economic growth.

In May 2013, just days before the start of the reporting period, Fed Chairman Ben Bernanke indicated in public remarks that U.S. monetary policymakers would begin to back away from its bond purchasing program sooner than most analysts had expected. Financial markets throughout the world reacted to these relatively hawkish comments with heightened volatility, causing stocks to lose value and longer-term interest rates to climb sharply. Indeed, investors’ revised expectations of stronger economic growth gained credence when the U.S. Department of Congress announced that U.S. GDP had expanded at a

2.5% annualized rate over the second quarter of the year, up from 1.1% in the first quarter. Moreover, June saw robust increases in home and automobile sales, expansions of the manufacturing and service sectors, and the creation of new 195,000 jobs.

Financial markets generally stabilized over the summer when investors came to recognize that the Fed’s plans to taper its quantitative easing program did not necessarily portend imminent increases in short-term interest rates. Still, labor markets continued to strengthen. In September, equity and fixed-income investors responded positively when the Fed unexpectedly refrained from reducing its monthly bond purchases due to lingering economic concerns, including weaker-than-expected employment data. However, it later was estimated that the U.S. economy had expanded at a relatively robust 4.1% annualized rate during the third quarter of the year.

October saw economic worries intensify in the midst of a 16-day U.S. government shutdown caused by Congress’s inability to agree on a funding resolution. At its October meeting, the

3      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Fed again postponed any cutbacks in quantitative easing, reflecting reduced expectations for economic growth over the near to intermediate term. November told a different story: the economy appeared to gain momentum as the unemployment rate slid and more than 200,000 new jobs were added. In addition, manufacturing activity increased at its fastest pace in two years, contributing to further increases in long-term rates and driving several broad measures of stock market performance to record highs.

FUND REVIEW

In spite of heightened volatility at the longer end of the bond market’s maturity range, the Fund continued to generate consistent and competitive levels of current income, albeit at levels commensurate with the Fed’s unchanged target for the federal funds rate. In addition, money market supply continues to be constrained as issuers look to lock in relatively cheap term financing further out on the yield curve. This puts additional downward pressure on money market yields.

In this environment, we maintained the Fund’s weighted average maturity in a range we considered to be in line with market averages. From a portfolio composition perspective, we continued to avoid repurchase agreements due to uncertainty surrounding potential regulatory changes. Instead, we primarily favored commercial paper issued by global banks that meet our stringent credit criteria.

STRATEGY & OUTLOOK

In light of recently positive economic data, we continue to expect the Fed to taper its quantitative easing program in the relatively near future. Nonetheless, we believe that the Fed will maintain its current target for short-term interest rates for some time to come, and money market yields could remain near current levels for much of 2014. Meanwhile, the outlook for U.S. fiscal and regulatory policies remained uncertain as of the reporting period’s end, suggesting to us that the appropriate strategy is to continue to focus on quality and liquidity. Therefore, we currently intend to maintain a roughly market-neutral weighted average maturity, and we expect to continue to focus on high-quality instruments from fundamentally strong issuers.

1. Adam Wilde became a Portfolio Manager in July 2013.

4      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Portfolio Allocation*

Certificates of Deposit	39.1%
Short-Term Notes/ Commercial Paper	37.0
Direct Bank Obligations	19.2
Investment Companies	4.7

Portfolio holdings and allocations are subject to change.

Percentages are as of November 29, 2013, and are based on the total market value of investments.

Performance*

CURRENT YIELD

For the 7-Day Period Ended 11/29/13

	With Compounding	Without Compounding
Class E (IOEXX)	0.09%	0.09%
Class L (IOLXX)	0.04	0.04
Class P (IOPXX)	0.01	0.01

CURRENT YIELD

For the Six Months Ended 11/29/13

	With Compounding	Without Compounding
Class E (IOEXX)	0.10%	0.10%
Class L (IOLXX)	0.05	0.05
Class P (IOPXX)	0.01	0.01

Compounded yields assume reinvestment of dividends. The seven-day yield without compounding is an annualized average daily yield of the Fund for the most recent seven days. The compounded seven-day average yield for 365 days is offered as a comparison to a savings account’s compounded interest rate. Unlike an investment in the Fund, the FDIC generally insures deposits in savings accounts.

Performance data quoted represents past performance, which does not guarantee future results. Yields include dividends in a hypothetical investment for the periods shown. Current performance may be lower or higher than the performance quoted. For more current performance data, call us at 1.800.645.2028. The Fund’s performance shown does not reflect the deduction of income taxes on an individual’s investment. The yields take into account voluntary fee waivers and/or expense reimbursements, without which yields would have been lower. Some of these undertakings may be modified or terminated at any time, as indicated in the Fund’s prospectus. Taxes may reduce your actual investment returns on income paid by the Fund. There is no guarantee that the Fund will maintain a positive yield.

*November 29, 2013, was the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes to Financial Statements.

5      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

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.

An investment in money market funds is neither insured nor guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the Fund.

The Fund’s investment strategy, allocations, 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 Fund and may be obtained by calling us at 1.800.645.2028 or visiting our website at oppenheimerfunds.com. Read prospectuses and summary prospectuses carefully before investing.

6      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Fund Expenses

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

The examples are based on an investment of $1,000.00 invested at the beginning of the period and held for the entire 6-month period ended November 29, 2013.

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

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

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

7      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Actual	Beginning Account Value June 1, 2013		Ending Account Value November 29, 2013		Expenses Paid During 6 Months Ended November 29, 2013
Class E	$	1,000.00	$	1,000.50	$	0.50
Class L		1,000.00		1,000.30		0.80
Class P		1,000.00		1,000.10		1.00
Hypothetical
(5% return before expenses)
Class E		1,000.00		1,024.43		0.50
Class L		1,000.00		1,024.13		0.81
Class P		1,000.00		1,023.93		1.01

Expenses are equal to the Fund’s annualized expense ratio for that class, multiplied by the average account value over the period, multiplied by 182/365 (to reflect the one-half year period). Those annualized expense ratios, excluding indirect expenses from affiliated funds, based on the 6-month period ended November 29, 2013 are as follows:

Class	Expense Ratios
Class E		0.10%
Class L		0.16
Class P		0.20

The expense ratios reflect voluntary waivers and/or reimbursements of expenses by the Fund’s Manager and Distributor. 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.

8      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS    November 29, 2013*     Unaudited

	Maturity Date**		Final Legal Maturity Date***		Principal Amount		Value
Certificates of Deposit—38.2%
Yankee Certificates of Deposit—38.2%
Aust & NZ Banking Group, Grand Cayman:
0.08%		12/3/13		12/3/13	$	100,000,000	$	100,000,000
0.08%		12/2/13		12/2/13		150,000,000		150,000,000
Bank of Montreal, Chicago:
0.18%		1/23/14		1/23/14		65,250,000		65,249,997
0.18%		1/3/14		1/3/14		50,000,000		50,000,000
Bank of Nova Scotia, Houston TX:
0.19%		2/14/14		2/14/14		100,000,000		100,000,000
0.19%		3/17/14		3/17/14		60,000,000		60,000,000
0.19%		2/19/14		2/19/14		50,000,000		50,000,000
0.21%		3/28/14		3/28/14		30,000,000		30,000,000
0.21%		5/14/14		5/14/14		50,000,000		50,000,000
0.234%1		12/27/13		11/26/14		45,000,000		45,000,000
Bank of Tokyo-Mitsubishi UFJ NY:
0.16%2		12/26/13		12/26/13		70,000,000		70,000,000
0.16%2		12/16/13		12/16/13		20,000,000		20,000,000
0.16%2		12/13/13		12/13/13		80,000,000		80,000,000
BNP Paribas, New York:
0.22%		1/13/14		1/13/14		42,000,000		42,000,000
0.23%		1/10/14		1/10/14		50,000,000		50,000,000
0.74%		1/15/14		1/15/14		67,000,000		67,000,000
DnB Bank ASA NY:
0.19%		1/8/14		1/8/14		70,000,000		70,000,000
0.205%		12/20/13		12/20/13		50,000,000		50,000,000
0.21%		1/3/14		1/3/14		58,200,000		58,200,000
DnB Bank ASA, Grand Cayman, 0.04%		12/2/13		12/2/13		60,000,000		60,000,000
Mitsubishi UFJ TR & BK NY, 0.16%		12/27/13		12/27/13		75,000,000		75,000,000
Nordea Bank Finland plc, New York:
0.215%		4/23/14		4/23/14		50,000,000		49,999,015
0.24%		2/19/14		2/19/14		5,000,000		5,000,000
Rabobank Nederland NV, New York:
0.23%		4/23/14		4/23/14		50,000,000		50,000,000
0.268%1		2/24/14		8/26/14		50,000,000		50,000,000
0.292%1		2/27/14		8/27/14		50,000,000		50,000,000
0.301%1		12/3/13		9/3/14		50,000,000		50,000,000
0.314%1		1/31/14		10/31/14		54,500,000		54,500,000
0.341%1		1/7/14		10/7/14		43,500,000		43,500,000
Royal Bank of Canada, New York:
0.276%1		12/24/13		6/24/14		66,000,000		66,000,000
0.32%1		12/2/13		2/3/14		100,000,000		100,000,000
Skandinaviska Enskilda Bank, New York:
0.19%		3/19/14		3/19/14		50,000,000		50,000,000
0.19%		3/12/14		3/12/14		25,000,000		25,000,000
0.195%		3/10/14		3/10/14		53,000,000		53,000,000
Skandinaviska Enskilda Banken, Grand Cayman, 0.06%		12/2/13		12/2/13		27,500,000		27,500,000
Sumitomo Mutsui Bank NY:
0.10%		12/6/13		12/6/13		88,200,000		88,200,000
0.10%		12/4/13		12/4/13		134,000,000		134,000,000
0.10%		12/3/13		12/3/13		55,000,000		55,000,000

9      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS     Unaudited / Continued

	Maturity Date**		Final Legal Maturity Date***		Principal Amount		Value
Yankee Certificates of Deposit Continued
Svenska Handelsbanken, Grand Cayman, 0.05%		12/2/13		12/2/13	$	159,000,000	$	159,000,000
Svenska Handelsbanken, New York:
0.21%		12/6/13		12/6/13		25,000,000		25,000,028
0.22%		12/2/13		12/2/13		50,000,000		50,000,000
0.24%		2/20/14		2/20/14		50,000,000		50,000,000
Toronto Dominion Bank, New York:
0.218%1		12/17/13		6/17/14		95,000,000		95,000,000
0.22%		4/22/14		4/22/14		50,000,000		50,000,000
0.26%		1/6/14		1/6/14		50,000,000		50,000,000
0.32%		4/2/14		4/2/14		25,000,000		25,003,350
Wells Fargo Bank NA:
0.238%1		12/20/13		11/20/14		100,000,000		100,000,000
0.239%1		12/5/13		9/5/14		65,500,000		65,500,000
0.248%		12/2/13		5/1/14		100,000,000		100,000,000
Total Certificates of Deposit (Cost $3,063,652,390)								3,063,652,390
Direct Bank Obligations—18.7%
Barclays US Funding LLC:
0.07%		12/4/13		12/4/13		52,000,000		51,999,798
0.07%		12/2/13		12/2/13		100,000,000		100,000,000
0.10%		12/6/13		12/6/13		68,400,000		68,399,240
Commonwealth Bank of Australia:
0.22%3		4/22/14		4/22/14		43,500,000		43,462,517
0.225%3		4/23/14		4/23/14		71,280,000		71,216,739
DnB Bank ASA:
0.18%3		1/27/14		1/27/14		41,300,000		41,288,436
0.324%1,3		1/23/14		1/23/14		55,900,000		55,909,984
Nordea Bank AB, 0.22%		3/12/14		3/12/14		100,000,000		99,938,889
Rabobank USA Financial Corp., 0.225%		3/6/14		3/6/14		25,830,000		25,814,825
Skandinaviska Enskilda BankenAB:
0.175%3		12/5/13		12/5/13		76,000,000		75,998,892
0.20%3		3/27/14		3/27/14		58,000,000		57,962,944
0.21%3		2/5/14		2/5/14		50,000,000		49,981,042
Societe Generale North America, Inc.:
0.105%		12/4/13		12/4/13		52,000,000		51,999,697
0.105%		12/3/13		12/3/13		100,000,000		99,999,708
Svenska Handelsbanken, Inc.:
0.215%3		4/2/14		4/2/14		54,000,000		53,960,977
0.24%3		2/24/14		2/24/14		50,000,000		49,972,000
Swedbank AB:
0.175%		3/11/14		3/11/14		19,000,000		18,990,856
0.198%		12/6/13		12/6/13		127,000,000		126,997,206
0.20%		12/3/13		12/3/13		70,920,000		70,919,606
0.205%		2/19/14		2/19/14		50,000,000		49,977,507
0.205%		2/24/14		2/24/14		40,000,000		39,980,867
Westpac Banking Corp.:
0.289%1,3		1/23/14		1/23/14		100,000,000		100,000,000
0.293%1,2,3		1/9/14		1/9/14		100,300,000		100,300,000
Total Direct Bank Obligations (Cost $1,505,071,730)								1,505,071,730

10      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

	Maturity Date**		Final Legal Maturity Date***		Principal Amount		Value
Short-Term Notes/Commercial Paper—36.0%
Banks—4.4%
Bank of Nova Scotia, New York, 0.215%		4/1/14		4/1/14	$	11,000,000	$	10,992,117
Bank of Nova Scotia, New York, 0.245%		8/26/14		8/26/14		37,700,000		37,631,496
Bank of Tokyo-Mitsubishi UFJ NY, 0.09%2		12/6/13		12/6/13		17,900,000		17,899,821
HSBC USA, Inc.:
0.215%		5/8/14		5/8/14		31,500,000		31,470,464
0.215%		3/18/14		3/18/14		54,250,000		54,215,657
0.22%		5/27/14		5/27/14		72,110,000		72,032,441
0.225%		4/23/14		4/23/14		50,000,000		49,955,625
0.23%		3/10/14		3/10/14		75,225,000		75,177,901
								349,375,522
Diversified Financial Services—1.8%
General Electric Capital Corp.:
0.24%		1/16/14		1/16/14		45,000,000		44,986,500
0.24%		1/17/14		1/17/14		100,000,000		99,969,334
								144,955,834
Leasing & Factoring—3.7%
American Honda Finance Corp., 0.28%1,2		12/5/13		12/5/13		62,257,000		62,257,000
Toyota Motor Credit Corp.:
0.208%		12/9/13		2/26/14		14,500,000		14,500,000
0.208%		12/31/13		2/25/14		60,000,000		60,000,000
0.23%		6/2/14		6/2/14		100,000,000		99,883,722
0.25%		2/28/14		2/28/14		61,200,000		61,162,600
								297,803,322
Municipal—4.6%
AARP Nts., Series 2001, 0.16%1		12/6/13		12/6/13		50,000,000		50,000,000
Baltimore, MD General Obligation Bonds, Series 2003C, 0.10%1		12/6/13		12/6/13		7,905,000		7,905,000
Calhoun Cnty. Navigation District Solid Waste Disposal Revenue Bonds, Formosa Plastics Corp., Series 2001, 0.09%1		12/6/13		12/6/13		12,500,000		12,500,000
Calhoun Port Authority, TX Revenue Bonds, Formosa Plastics Corp. America, Series 2012, 0.09%1		12/6/13		12/6/13		50,000,000		50,000,000
Capital Market Access Co. LC Bonds, Carteret Investment Assn. LLC, Series 2008, 0.18%1		12/6/13		12/6/13		6,740,000		6,740,000
Charlotte, NC Certificates of Participation, NASCAR Hall of Fame Facilities, Series 09D, 0.13%1		12/6/13		12/6/13		93,595,000		93,595,000
District of Columbia Revenue Bonds, American Immigration Lawyers, Series 07, 0.10%1		12/6/13		12/6/13		11,575,000		11,575,000
Johnson, TN Health & Education Facilities, Mountain States Health, Series 2007B-1, 0.16%1		12/6/13		12/6/13		2,995,000		2,995,000
Johnson, TN Health & Education Facilities, Mountain States Health, Series 2013B, 0.14%1		12/6/13		12/6/13		11,075,000		11,075,000
Lewisburg, TN Industrial Development Board, Waste Management of Tennessee Project, Series 2003, 0.09%1		12/6/13		12/6/13		25,000,000		25,000,000

11      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS     Unaudited / Continued

	Maturity Date**		Final Legal Maturity Date***		Principal Amount		Value
Municipal Continued
Macon-Bibb Cnty. GA Industrial Development Authority Revenue Bonds, Bass Pro Outdoor World, Series 2005, 0.20%1		12/6/13		12/6/13	$	18,200,000	$	18,200,000
OH Higher Education Facilities Commission, Xavier University 2008 Project, Series B, 0.16%1		12/6/13		12/6/13		20,480,000		20,480,000
Power Cnty., ID Industrial Development Corp., FMC Corp. Project, Series 2001, 0.10%1		12/6/13		12/6/13		16,000,000		16,000,000
SC Jobs Economic Development Authority Bonds, South Atlantic Canners, Inc., Series 2001, 0.20%1		12/6/13		12/6/13		5,000,000		5,000,000
St. Paul, MN Bonds, Rivercentre Arena Project, Series 2009A, 0.17%1		12/6/13		12/6/13		15,700,000		15,700,000
Tift Cnty. Development Authority Industrial Development Revenue Bonds, Heatcraft Refrigeration Products, Series 2008B, 0.17%1		12/6/13		12/6/13		11,700,000		11,700,000
Trinitas Hospital Bonds, Series 2006, 0.18%1		12/6/13		12/6/13		13,285,000		13,285,000
								371,750,000
Personal Products—0.6%
Reckitt Benckiser Treasury Services plc, 0.291%3		7/1/14		7/1/14		50,000,000		49,915,014
Receivables Finance—9.0%
Alpine Securitization Corp.:
0.07%		12/3/13		12/3/13		100,000,000		99,999,806
0.12%		12/20/13		12/20/13		12,170,000		12,169,270
0.12%		12/17/13		12/17/13		107,300,000		107,294,635
0.12%		12/19/13		12/19/13		34,000,000		33,998,073
Barton Capital Corp.:
0.194%3		4/7/14		4/7/14		50,000,000		50,000,000
0.20%3		4/4/14		4/4/14		50,000,000		50,000,000
Fairway Finance Corp.:
0.17%3		2/24/14		2/24/14		25,000,000		24,990,083
0.17%3		12/9/13		12/9/13		25,000,000		24,999,174
0.17%3		2/26/14		2/26/14		53,037,000		53,015,461
Gotham Funding Corp.:
0.15%3		12/17/13		12/17/13		3,906,000		3,905,756
0.15%3		12/18/13		12/18/13		8,411,000		8,410,439
Jupiter Securitization Co. LLC:
0.23%3		5/7/14		5/7/14		25,000,000		24,975,083
0.23%3		4/29/14		4/29/14		50,000,000		49,952,722
0.23%3		4/24/14		4/24/14		35,000,000		34,968,024
0.23%3		4/28/14		4/28/14		50,000,000		49,953,042
0.24%3		2/24/14		2/24/14		15,000,000		14,991,600
0.24%3		12/6/13		12/6/13		22,000,000		21,999,413
Old Line Funding Corp., 0.21%3		1/21/14		1/21/14		50,000,000		49,985,417
Victory Receivables Corp., 0.15%3		12/20/13		12/20/13		7,763,000		7,762,418
								723,370,416
Special Purpose Financial—11.9%
Anglesea Funding LLC:
0.168%		12/2/13		12/2/13		58,000,000		58,000,000
0.18%2		12/3/13		12/3/13		45,000,000		44,999,775

12      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

	Maturity Date**		Final Legal Maturity Date***		Principal Amount		Value
Special Purpose Financial Continued
Collateralized Commercial Paper II Co. LLC,
0.30%2		1/24/14		1/24/14	$	78,000,000	$	77,965,550
Concord Minutemen Cap. Corp. LLC:
0.22%		2/13/14		2/13/14		25,000,000		24,988,847
0.22%		2/14/14		2/14/14		30,000,000		29,986,433
0.22%		2/4/14		2/4/14		50,000,000		49,980,445
0.22%		2/6/14		2/6/14		68,500,000		68,472,372
Crown Point Capital Co.:
0.21%		1/3/14		1/3/14		64,000,000		63,988,053
0.21%		1/2/14		1/2/14		59,000,000		58,989,331
0.22%		1/17/14		1/17/14		40,000,000		39,988,756
0.22%		1/22/14		1/22/14		10,000,000		9,996,883
FCAR Owner Trust I, 0.20%		3/4/14		3/4/14		56,500,000		56,471,122
Govco LLC:
0.24%3		2/3/14		2/3/14		100,500,000		100,457,851
0.24%3		2/11/14		2/11/14		37,400,000		37,382,297
0.24%3		2/6/14		2/6/14		68,000,000		67,970,080
Legacy Capital LLC:
0.17%		12/2/13		12/2/13		18,000,000		18,000,000
0.17%		12/4/13		12/4/13		34,000,000		33,999,679
Lexington Parker Capital Co. LLC:
0.20%3		1/7/14		1/7/14		19,000,000		18,996,200
0.20%3		1/14/14		1/14/14		48,000,000		47,988,533
Ridgefield Funding Co. LLC, 0.259%1		12/9/13		4/7/14		50,000,000		50,000,000
								958,622,207
Total Short-Term Notes/Commercial Paper (Cost $2,895,792,315)								2,895,792,315
Investment Companies—4.6%
Dreyfus Institutional Cash Advantage Fund, 0.06%4		12/2/13		12/2/13		200,009,042		200,009,042
Prime Money Market Fund RBC Institutional, Cl. 1, 0.02%4		12/2/13		12/2/13		166,172,472		166,172,471
Total Investment Companies (Cost $366,181,513)								366,181,513
Total Investments, at Value (Cost $7,830,697,948)						97.5%		7,830,697,948
Assets in Excess of Other Liabilities						2.5		201,682,107
Net Assets						100.0%	$	8,032,380,055

Footnotes to Statement of Investments

Short-term notes and direct bank obligations are generally traded on a discount basis; the interest rate shown is the discount rate received by the Fund at the time of purchase. Other securities normally bear interest at the rates shown.

*November 29, 2013 represents the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes.

**The Maturity Date represents the date used to calculate the Fund’s weighted average maturity as determined under Rule 2a-7.

13      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS     Unaudited / Continued

Footnotes to Statement of Investments (Continued)

***If different from the Maturity Date, the Final Legal Maturity Date includes any maturity date extensions which may be affected at the option of the issuer or unconditional payments of principal by the issuer which may be affected at the option of the Fund, and represents the date used to calculate the Fund’s weighted average life as determined under Rule 2a-7.

1. Represents the current interest rate for a variable or increasing rate security.

2. Represents securities sold under Rule 144A, which are exempt from registration under the Securities Act of 1933, as amended. These securities have been determined to be liquid under guidelines established by the Board of Trustees. These securities amount to $473,422,146 or 5.89% of the Fund’s net assets as of November 29, 2013.

3. Security issued in an exempt transaction without registration under the Securities Act of 1933. Such securities amount to $1,492,672,138 or 18.58% of the Fund’s net assets, and have been determined to be liquid pursuant to guidelines adopted by the Board of Trustees.

4. Rate shown is the 7-day yield as of November 29, 2013.

See accompanying Notes to Financial Statements.

14      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF

ASSETS AND LIABILITIES    November 29, 2013¹       Unaudited

Assets
Investments, at value (cost $7,830,697,948)—see accompanying statement of investments	$	7,830,697,948
Cash		201,708,128
Receivables and other assets:
Interest and dividends		1,367,592
Shares of beneficial interest sold		133,980
Other		373,241
Total assets		8,034,280,889
Liabilities
Payables and other liabilities:
Dividends		1,025,653
Trustees’ compensation		735,142
Transfer and shareholder servicing agent fees		48,753
Shareholder communications		13,353
Investments purchased		9,287
Service plan fees		2,076
Other		66,570
Total liabilities		1,900,834
Net Assets	$	8,032,380,055
Composition of Net Assets
Par value of shares of beneficial interest	$	8,033,413
Additional paid-in capital		8,025,379,427
Accumulated net investment loss		(1,144,588	)
Accumulated net realized gain on investments		111,803
Net Assets	$	8,032,380,055
Net Asset Value Per Share
Class E Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $6,809,407,206 and 6,810,280,525 shares of beneficial interest outstanding)		$1.00
Class L Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $1,204,742,567 and 1,204,917,019 shares of beneficial interest outstanding)		$1.00
Class P Shares:
Net asset value, redemption price (excludes applicable contingent deferred sales charge) and offering price per share (based on net assets of $18,230,282 and 18,215,296 shares of beneficial interest outstanding)		$1.00

1. November 29, 2013 represents the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

15      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF

OPERATIONS    For the Six Months Ended November 29, 2013¹       Unaudited

Investment Income
Interest	$	7,280,045
Dividends		18,850
Total investment income		7,298,895
Expenses
Management fees		3,544,348
Service plan fees—Class P		16,804
Transfer and shareholder servicing agent fees:
Class L		236,511
Class P		3,357
Shareholder communications:
Class E		5,638
Class L		23,236
Trustees’ compensation		76,780
Custodian fees and expenses		21,585
Other		77,819
Total expenses		4,006,078
Less waivers and reimbursements of expenses		(13,838	)
Net expenses		3,992,240
Net Investment Income		3,306,655
Net Realized Loss on Investments		(5,160	)
Net Increase in Net Assets Resulting from Operations	$	3,301,495

1. November 29, 2013 represents the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

16      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENTS OF CHANGES IN NET ASSETS

	Six Months Ended November 29, 20131 (Unaudited)			Year Ended May 31, 2013
Operations
Net investment income	$	3,306,655		$	9,924,591
Net realized gain (loss)		(5,160	)		116,963
Net increase in net assets resulting from operations		3,301,495			10,041,554
Dividends and/or Distributions to Shareholders
Dividends from net investment income:
Class E		(3,705,202	)		(9,339,023	)
Class L		(276,452	)		(688,157	)
Class P		(899	)		(7,672	)
		(3,982,553	)		(10,034,852	)
Beneficial Interest Transactions
Net increase in net assets resulting from beneficial interest transactions:
Class E		1,034,870,078			416,157,397
Class L		246,641,126			380,342,746
Class P		3,538,791			4,811,503
		1,285,049,995			801,311,646
Net Assets
Total increase		1,284,368,937			801,318,348
Beginning of period		6,748,011,118			5,946,692,770
End of period (including accumulated net investment loss of $1,144,588 and $468,690, respectively)	$	8,032,380,055		$	6,748,011,118

1. November 29, 2013 represents the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

17      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

FINANCIAL HIGHLIGHTS

Class E	Six Months Ended November 29, 20131 (Unaudited)			Year Ended May 31, 2013			Year Ended May 31, 2012			Year Ended May 31, 2011			Year Ended May 31, 2010			Year Ended May 31, 2009
Per Share Operating Data
Net asset value, beginning of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Income (loss) from investment operations—net investment income and net realized gain2		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		0.02
Dividends and/or distributions to shareholders:
Dividends from net investment income		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		(0.02)
Distributions from net realized gain		0.00			0.00			0.00			0.00	3		0.00			0.00	3
Total dividends and/or distributions to shareholders		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		(0.02)
Net asset value, end of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Total Return, at Net Asset Value4		0.05%			0.17%			0.19%			0.23%			0.28%			1.96%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	6,809,407		$	5,775,156		$	5,358,991		$	7,080,092		$	5,285,125		$	6,608,401
Average net assets (in thousands)	$	6,138,124		$	5,689,719		$	6,085,688		$	5,984,276		$	5,755,335		$	5,649,134
Ratios to average net assets:5
Net investment income		0.10%			0.16%			0.18%			0.22%			0.28%			1.89%
Total expenses		0.10%			0.11%			0.11%			0.11%			0.12%			0.13%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.10%			0.11%			0.11%			0.11%			0.12%			0.13%

18      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

1. November 29, 2013 represents the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes.

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

3. Less than $0.005 per share.

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. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

5. Annualized for periods less than one full year.

See accompanying Notes to Financial Statements.

19      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

FINANCIAL HIGHLIGHTS    Continued

Class L	Six Months Ended November 29, 20131 (Unaudited)			Year Ended May 31, 2013			Year Ended May 31, 2012			Year Ended May 31, 2011			Year Ended May 31, 2010			Year Ended May 31, 2009
Per Share Operating Data
Net asset value, beginning of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Income (loss) from investment operations—net investment income and net realized gain2		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		0.02
Dividends and/or distributions to shareholders:
Dividends from net investment income		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		(0.02)
Distributions from net realized gain		0.00			0.00			0.00			0.00	3		0.00			0.00	3
Total dividends and/or distributions to shareholders		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		(0.02)
Net asset value, end of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Total Return, at Net Asset Value4		0.03%			0.10%			0.12%			0.17%			0.23%			1.95%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	1,204,743		$	958,163		$	577,822		$	879,941		$	763,826		$	1,457,981
Average net assets (in thousands)	$	948,321		$	693,086		$	891,161		$	948,365		$	1,766,105		$	1,219,384
Ratios to average net assets:5
Net investment income		0.05%			0.10%			0.12%			0.17%			0.23%			1.97%
Total expenses		0.16%			0.17%			0.17%			0.17%			0.17%			0.15%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.16%			0.17%			0.17%			0.17%			0.17%			0.14%

1. November 29, 2013 represents the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes.

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

3. Less than $0.005 per share.

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. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

5. Annualized for periods less than one full year.

See accompanying Notes to Financial Statements.

20      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Class P	Six Months Ended November 29, 20131 (Unaudited)			Year Ended May 31, 2013			Year Ended May 31, 2012			Year Ended May 31, 2011			Year Ended May 31, 2010			Year Ended May 31, 2009
Per Share Operating Data
Net asset value, beginning of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Income (loss) from investment operations—net investment income and net realized gain2		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		0.02
Dividends and/or distributions to shareholders:
Dividends from net investment income		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		(0.02)
Distributions from net realized gain		0.00			0.00			0.00			0.00	3		0.00			0.00	3
Total dividends and/or distributions to shareholders		0.00	3		0.00	3		0.00	3		0.00	3		0.00	3		(0.02)
Net asset value, end of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Total Return, at Net Asset Value4		0.01%			0.07%			0.09%			0.13%			0.18%			1.88%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	18,230		$	14,692		$	9,880		$	10,307		$	8,252		$	17,823
Average net assets (in thousands)	$	13,540		$	12,903		$	8,150		$	8,974		$	12,254		$	139,489
Ratios to average net assets:5
Net investment income		0.01%			0.06%			0.09%			0.12%			0.19%			2.26%
Total expenses		0.40%			0.41%			0.40%			0.41%			0.53%			0.39%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.20%			0.21%			0.20%			0.21%			0.22%			0.18%

1. November 29, 2013 represents the last business day of the Fund’s reporting period. See Note 1 of the accompanying Notes.

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

3. Less than $0.005 per share.

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. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

5. Annualized for periods less than one full year.

See accompanying Notes to Financial Statements.

21      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

NOTES TO

FINANCIAL STATEMENTSNovember 29, 2013    Unaudited

1. Significant Accounting Policies

Oppenheimer Institutional Money Market Fund (the “Fund”) is registered under the Investment Company Act of 1940, as amended, as a diversified open-end management investment company. The Fund’s investment objective is to seek income consistent with stability of principal. 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. As of November 29, 2013, approximately 87% of the shares of the Fund were owned by the Manager, other funds advised or sub-advised by the Manager or an affiliate of the Manager.

The Fund offers Class E, Class L and Class P shares. Class E and Class L shares are sold at net asset value per share without any initial sales charge. Class E shares are only offered to other Oppenheimer Funds, the Manager and their affiliates. Class P shares will normally be sold at net asset value per share without any initial sales charge and are subject to a service plan. Class L and Class P shares are offered directly to institutional investors and may only be sold through an investment professional. Brokers or other investment professionals that offer Class L and Class P shares may impose charges on those accounts. 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.

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

Semiannual Period. The last day of the Fund’s semiannual period was the last day the New York Stock Exchange was open for trading. 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.

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

Federal Taxes. The Fund intends to comply with provisions of the Internal Revenue Code applicable to regulated investment companies and to distribute substantially all of its investment company taxable income to shareholders. Therefore, no federal income or excise tax provision is required. The Fund files income tax returns in U.S. federal and applicable state jurisdictions. The statute of limitations on the Fund’s tax return filings generally remain open for the three preceding fiscal reporting period ends.

During the fiscal year end May 31, 2013, the Fund did not utilize any capital loss carryforward to offset capital gains realized in that fiscal year.

22      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

1. Significant Accounting Policies (Continued)

Trustees’ Compensation. The Fund has adopted an unfunded retirement plan (the “Plan”) for the Fund’s independent trustees. Benefits are based on years of service and fees paid to each trustee during their period of service. The Plan was frozen with respect to adding new participants effective December 31, 2006 (the “Freeze Date”) and existing Plan Participants as of the Freeze Date will continue to receive accrued benefits under the Plan. Active independent trustees as of the Freeze Date have each elected a distribution method with respect to their benefits under the Plan. During the six months ended November 29, 2013, the Fund’s projected benefit obligations, payments to retired trustees and accumulated liability were as follows:

Projected Benefit Obligations Increased	$	14,036
Payments Made to Retired Trustees		—
Accumulated Liability as of November 29, 2013		348,428

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

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 distributions, if any, are declared daily and paid monthly. Capital gain distributions, if any, are declared and paid annually but may be paid at other times to maintain the net asset value per share at $1.00. The tax character of distributions is determined as of the Fund’s fiscal year end. Therefore, a portion of the Fund’s distributions made to shareholders prior to the Fund’s fiscal year end may ultimately be categorized as a tax return of capital.

Investment Income. Interest income is recognized on an accrual basis. Discount and premium, which are included in interest income on the Statement of Operations, are amortized or accreted daily.

Custodian Fees. “Custodian fees and expenses” in the Statement of Operations may include interest expense incurred by the Fund on any cash overdrafts of its custodian account during the period. Such cash overdrafts may result from the effects of failed trades in portfolio securities and from cash outflows resulting from unanticipated shareholder redemption

23      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

NOTES TO FINANCIAL STATEMENTS    Unaudited / Continued

1. Significant Accounting Policies (Continued)

activity. The Fund pays interest to its custodian on such cash overdraft at a rate equal to the 1 Month LIBOR Rate plus 2.00%. The “Reduction to custodian expenses” line item, if applicable, represents earnings on cash balances maintained by the Fund during the period. Such interest expense and other custodian fees may be paid with these earnings.

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

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

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

2. Securities Valuation

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

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

Valuation Methods and Inputs

Securities are valued at cost adjusted by the amortization of discount or premium to maturity (amortized cost), which approximates market value. If amortized cost is determined not to approximate market value, the fair value of the portfolio securities will be determined under procedures approved by the Fund’s Board of Trustees.

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

24      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

2. Securities Valuation (Continued)

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.)

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).

25      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

NOTES TO FINANCIAL STATEMENTS    Unaudited / Continued

2. Securities Valuation (Continued)

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 November 29, 2013 based on valuation input level:

	Level 1— Unadjusted Quoted Prices		Level 2— Other Significant Observable Inputs		Level 3— Significant Unobservable Inputs		Value
Assets Table
Investments, at Value:
Certificates of Deposit	$	—	$	3,063,652,390	$	—	$	3,063,652,390
Direct Bank Obligations		—		1,505,071,730		—		1,505,071,730
Short-Term Notes/Commercial Paper		—		2,895,795,315		—		2,895,792,315
Investment Companies		—		366,181,513		—		366,181,513
Total Assets	$	—	$	7,830,697,948	$	—	$	7,830,697,948

3. Shares of Beneficial Interest

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

				Six Months Ended						Year Ended
				November 29, 2013						May 31, 2013
	Shares			Amount			Shares			Amount
Class E
Sold		27,627,767,827		$	27,627,767,827			40,742,390,279		$	40,742,390,279
Dividends and/or distributions reinvested		390,849			390,849			1,327,435			1,327,435
Redeemed		(26,593,288,598	)		(26,593,288,598	)		(40,327,560,317	)		(40,327,560,317	)
Net increase		1,034,870,078		$	1,034,870,078			416,157,397		$	416,157,397
Class L
Sold		14,922,179,248		$	14,922,179,248			26,527,000,500		$	26,527,000,500
Dividends and/or distributions reinvested		155,142			155,142			580,228			580,228
Redeemed		(14,675,693,264	)		(14,675,693,264	)		(26,147,237,982	)		(26,147,237,982	)
Net increase		246,641,126		$	246,641,126			380,342,746		$	380,342,746
Class P
Sold		5,000,000		$	5,000,000			20,303,807		$	20,303,807
Dividends and/or distributions reinvested		564			564			5,539			5,539
Redeemed		(1,461,773	)		(1,461,773	)		(15,497,843	)		(15,497,843	)
Net increase		3,538,791		$	3,538,791			4,811,503		$	4,811,503

26      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

4. 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 of 0.10%.

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. Fees incurred by the Fund with respect to these services are detailed in the Statement of Operations.

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.

Service Plan for Class P Shares. The Fund has adopted a Service Plan (the “Plan”) for Class P shares under Rule 12b-1 of the Investment Company Act of 1940. Under the Plan, the Fund reimburses the Distributor for a portion of its costs incurred for services provided to accounts that hold Class P shares. Reimbursement is made periodically at an annual rate of up to 0.25% of the average annual net assets of Class P 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 P shares. Any unreimbursed expenses the Distributor incurs with respect to Class P 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.

Waivers and Reimbursements of Expenses. The Manager has voluntarily agreed to waive fees and/or reimburse the Fund for certain expenses in order to limit “Expenses after waivers, payments and/or reimbursements and reduction to custodian fees” (excluding (i) interest, taxes, dividends tied to short sales, brokerage commissions, and other expenditures which are capitalized in accordance with generally accepted accounting principles: (ii) expenses incurred directly or indirectly by the Fund as a result of investments in other investment companies, wholly-owned subsidiaries and pooled investment vehicles; (iii) certain other expenses attributable to, and incurred as a result of, a Fund’s investments; and (iv)

27      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

NOTES TO FINANCIAL STATEMENTS    Unaudited / Continued

4. Fees and Other Transactions with Affiliates (Continued)

other extraordinary expenses (including litigation expenses) not incurred in the ordinary course of the Fund’s business) to annual rates of 0.15% for Class E shares, 0.19% for Class L shares and 0.24% for Class P shares calculated on the daily net assets of the Fund.

The Manager has also voluntarily undertaken to waive management fees and/or reimburse expenses (but not below zero) to the extent necessary to assist the Fund in attempting to maintain a positive yield. There is no guarantee that the Fund will maintain a positive yield. For the six months ended November 29, 2013, the Manager waived fees and/or reimbursed the Fund $395.

The Distributor has voluntarily undertaken to waive the fees payable under the Service Plan for Class P shares so that those fees are limited to 0.05% of the average annual net assets for Class P shares of the Fund. For the six months ended November 29, 2013, the Distributor waived $13,443 for Class P shares.

The Manager is permitted to recapture previously waived and/or reimbursed fees in any given fiscal year if the recapture would not: 1) cause the Fund to generate a negative daily yield, and 2) exceed amounts previously waived and/or reimbursed under this arrangement during the current and prior three fiscal years. The reimbursement to the Manager of such previous waivers and reimbursements would not include any portion of distribution and/or service fees. As of November 29, 2013, the following waived and/or reimbursed amounts are eligible for recapture:

Expiration Date

May 31, 2016

$395

The Manager has not recaptured any previously waived and/or reimbursed amounts during the six months ended November 29, 2013.

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

5. Pending Litigation

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

28      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

5. Pending Litigation (Continued)

On August 26, 2013, the parties in six of these lawsuits executed a memorandum of understanding setting forth the terms of proposed settlements of those actions. The proposed settlements are subject to a variety of contingencies, including the execution of settlement agreements, which will require preliminary and final approval by the court. The proposed settlements do not resolve a seventh outstanding lawsuit relating to Oppenheimer California Municipal Fund.

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

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

29      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

NOTES TO FINANCIAL STATEMENTS    Unaudited / Continued

5. Pending Litigation (Continued)

breach of contract against the defendants and sought compensatory damages, costs and disbursements, including attorney fees. On November 8, 2013, the parties filed a stipulation of discontinuance dismissing the lawsuit with prejudice.

OFI believes the lawsuits and appeals described above are without legal merit and, with the exception of actions it has settled, is defending against them vigorously. While it is premature to render any opinion as to the outcome in these lawsuits, or whether any costs that the Defendant Funds may bear in defending the suits might not be reimbursed by insurance, OFI believes that these suits should not impair the ability of OFI or the Distributor to perform their respective duties to the Fund, and that the outcome of all of the suits together should not have any material effect on the operations of any of the Oppenheimer mutual funds.

30      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

BOARD APPROVAL OF THE FUND’S INVESTMENT ADVISORY

AND SUB-ADVISORY AGREEMENTS    Unaudited

The Fund has entered into an investment advisory agreement with OFI Global Asset Management, Inc. (“OFI Global” or the “Adviser”), a wholly-owned subsidiary of OppenheimerFunds, Inc. (“OFI” or the “Sub-Adviser”) (“OFI Global” and “OFI” together the “Managers”) and OFI Global has entered into a sub-advisory agreement with OFI whereby OFI provides investment sub-advisory services to the Fund (collectively, the “Agreements”). Each year, the Board of Trustees (the “Board”), including a majority of the independent Trustees, is required to determine whether to renew the Agreements. The Investment Company Act of 1940, as amended, requires that the Board request and evaluate, and that the Managers provide, such information as may be reasonably necessary to evaluate the terms of the Agreements. The Board employs an independent consultant to prepare a report that provides information, including comparative information that the Board requests for that purpose. In addition to in-person meetings focused on this evaluation, the Board receives information throughout the year regarding Fund services, fees, expenses and performance.

The Adviser, Sub-Adviser and the independent consultant provided information to the Board on the following factors: (i) the nature, quality and extent of the Managers’ services, (ii) the investment performance of the Fund and the Managers, (iii) the fees and expenses of the Fund, including comparative expense information, (iv) the profitability of the Managers and their affiliates, including an analysis of the cost of providing services, (v) whether economies of scale are realized as the Fund grows and whether fee levels reflect these economies of scale for Fund investors and (vi) other benefits to the Managers from their relationship with the Fund. The Board was aware that there are alternatives to retaining the Managers.

Outlined below is a summary of the principal information considered by the Board as well as the Board’s conclusions.

Nature, Quality and Extent of Services. The Board considered information about the nature, quality and extent of the services provided to the Fund and information regarding the Managers’ key personnel who provide such services. The Sub-Adviser’s duties include providing the Fund with the services of the portfolio managers and the Sub-Adviser’s investment team, who provide research, analysis and other advisory services in regard to the Fund’s investments; securities trading services; oversight of third-party service providers; monitoring compliance with applicable Fund policies and procedures and adherence to the Fund’s investment restrictions; and risk management. The Managers are responsible for providing certain administrative services to the Fund as well. Those services include providing and supervising all administrative and clerical personnel who are necessary in order to provide effective corporate administration for the Fund; compiling and maintaining records with respect to the Fund’s operations; preparing and filing reports required by the Securities and Exchange Commission; preparing periodic reports regarding the operations of the Fund for its shareholders; preparing proxy materials for shareholder meetings; and preparing the registration statements required by Federal and state securities laws for the sale of the Fund’s shares. The Managers also provide the Fund with office space, facilities and equipment.

The Board also considered the quality of the services provided and the quality of the Managers’ resources that are available to the Fund. The Board took account of the fact that the Sub-Adviser has had over fifty years of experience as an investment adviser and that its assets nder management rank it among the top mutual fund managers in the United States. The Board evaluated the Sub-Adviser’s advisory, administrative, accounting, legal, compliance

31      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

BOARD APPROVAL OF THE FUND’S INVESTMENT ADVISORY

AND SUB-ADVISORY AGREEMENTS    Unaudited / Continued

services and risk management, and information the Board has received regarding the experience and professional qualifications of the Managers’ key personnel and the size and functions of its staff. In its evaluation of the quality of the portfolio management services provided, the Board considered the experience of Christopher Proctor and Adam Wilde, the portfolio managers for the Fund, and the Sub-Adviser’s investment team and analysts. The Board members also considered the totality of their experiences with the Managers as directors or trustees of the Fund and other funds advised by the Managers. The Board considered information regarding the quality of services provided by affiliates of the Managers, which its members have become knowledgeable about in connection with the renewal of the Fund’s service agreements. The Board concluded, in light of the Managers’ experience, reputation, personnel, operations and resources that the Fund benefits from the services provided under the Agreement.

Investment Performance of the Fund, the Adviser and the Sub-Adviser. Throughout the year, the Adviser and the Sub-Adviser provided information on the investment performance of the Fund, the Adviser and the Sub-Adviser, including comparative performance information. The Board also reviewed information, prepared by the Adviser, the Sub-Adviser and the independent consultant, comparing the Fund’s historical performance to its benchmark and to the performance of other retail money market-taxable funds. The Board noted that the Fund’s one-year, three-year, and five-year performance was better than its category median.

Costs of Services by the Adviser. The Board reviewed the fees paid to the Adviser and the other expenses borne by the Fund. The Board also considered the comparability of the fees charged and the services provided to the Fund to the fees and services for other clients or accounts advised by the Adviser. The independent consultant provided comparative data in regard to the fees and expenses of the Fund and other retail front-end load money market-taxable funds with comparable asset levels and distribution features. After discussions with the Board, the Adviser has agreed to voluntarily waive fees and/or reimburse the Fund for certain expenses in order to limit Total Annual Fund Operating Expenses (excluding (i) interest, taxes, dividends tied to short sales, brokerage commissions, and other expenditures which are capitalized in accordance with generally accepted accounting principles; (ii) expenses incurred directly or indirectly by the Fund as a result of investments in other investment companies, wholly-owned subsidiaries and pooled investment vehicles; (iii) certain other expenses attributable to, and incurred as a result of, a Fund’s investments; and (iv) other extraordinary expenses (including litigation expenses) not incurred in the ordinary course of the Fund’s business) to annual rates of 0.15% for Class E shares, 0.19% for Class L shares, and 0.24% for Class P shares, as calculated on the daily net assets of the Fund. The Adviser has also voluntarily undertaken to waive management fees and/or reimburse expenses to the extent necessary to assist the Fund in attempting to maintain a positive yield. Each of these fee waivers and/or expense reimbursements may be amended or withdrawn at any time, with approval of the Board, without prior notice to shareholders. The Fund’s contractual management fees and total expenses were lower than its peer group median and category median.

32      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Economies of Scale and Profits Realized by the Adviser and Sub-Adviser. The Board considered information regarding the Managers’ costs in serving as the Fund’s investment adviser and sub-adviser, including the costs associated with the personnel and systems necessary to manage the Fund, and information regarding the Managers’ profitability from their relationship with the Fund. The Board reviewed whether the Managers may realize economies of scale in managing and supporting the Fund and whether those economies of scale benefit the Fund’s shareholders at the current level of Fund assets in relation to its management fee.

Other Benefits to the Managers. In addition to considering the profits realized by the Managers, the Board considered information that was provided regarding the direct and indirect benefits the Managers receive as a result of their relationship with the Fund, including compensation paid to the Managers’ affiliates. The Board also considered that the Managers must be able to pay and retain experienced professional personnel at competitive rates to provide quality services to the Fund.

Conclusions. These factors were also considered by the independent Trustees meeting separately from the full Board, assisted by experienced counsel to the Fund and to the independent Trustees. Fund counsel and the independent Trustees’ counsel are independent of the Managers within the meaning and intent of the Securities and Exchange Commission Rules.

Based on its review of the information it received and its evaluations described above, the Board, including a majority of the independent Trustees, decided to continue the Agreements through September 30, 2014. In arriving at its decision, the Board did not identify any factor or factors as being more important than others, but considered all of the above information, and considered the terms and conditions of the Agreements, including the management fees, in light of all the surrounding circumstances.

33      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

SPECIAL SHAREHOLDER MEETING     Unaudited

On June 21, 2013, a shareholder meeting of Oppenheimer Institutional Money Market Fund (the “Fund”) was held at which the twelve Trustees identified below were elected to the Fund (Proposal No. 1). At the meeting the sub-proposals below (Proposal No. 2 (including all of its sub-proposals)) and an Agreement and Plan of Reorganization to reorganize the Fund into a Delaware statutory trust (Proposal No. 3) were approved as described in the Fund’s proxy statement dated April 12, 2013. The following is a report of the votes cast:

Nominee/Proposal	For		Withheld
Trustees
Brian F. Wruble		5,669,203,705		0
David K. Downes		5,669,203,705		0
Matthew P. Fink		5,669,203,705		0
Edmund Giambastiani, Jr.		5,669,203,705		0
Phillip A. Griffiths		5,669,203,705		0
Mary F. Miller		5,669,203,705		0
Joel W. Motley		5,669,203,705		0
Joanne Pace		5,669,203,705		0
Mary Ann Tynan		5,669,203,705		0
Joseph M. Wikler		5,669,203,705		0
Peter I. Wold		5,669,203,705		0
William F. Glavin, Jr.		5,669,203,705		0
2a: Proposal to revise the fundamental policy relating to borrowing
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657
2b-1: Proposal to revise the fundamental policy relating to concentration of investments
For	Against		Abstain
5,495,206,048		0		173,997,657
2c-1: Proposal to remove the fundamental policy relating to diversification of investments
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657
2c-2: Proposal to remove the additional fundamental policy relating to diversification of investments
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657
2d: Proposal to revise the fundamental policy relating to lending
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657
2e: Proposal to remove the additional fundamental policy relating to estate and commodities
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657
2f: Proposal to revise the fundamental policy relating to senior securities
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657

34      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

2g: Proposal to remove the additional fundamental policy relating to underwriting
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657
2r: Proposal to convert the Fund’s investment objective from fundamental to non-fundamental
For	Against		Abstain
5,173,547,753		321,658,295		173,997,657
2s: Proposal to approve a change in the Fund’s investment objective
For	Against		Abstain
5,495,206,048		0		173,997,657
Proposal 3: To approve an Agreement and Plan of Reorganization that provides for the reorganization of a Fund from a Maryland corporation or Massachusetts business trust, as applicable, into a Delaware statutory trust.
For	Against		Abstain
5,347,545,411		321,658,295		0

35      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

PORTFOLIO PROXY VOTING POLICIES AND PROCEDURES;

UPDATES TO STATEMENTS OF INVESTMENTS    Unaudited

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

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

Householding—Delivery of Shareholder Documents

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

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

36      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

OPPENHEIMER

INSTITUTIONAL MONEY MARKET FUND

Trustees and Officers	Brian F. Wruble, Chairman of the Board of Trustees and Trustee
	David K. Downes, Trustee
	Matthew P. Fink, Trustee
	Edmund P. Giambastiani, Jr., Trustee
	Phillip A. Griffiths, Trustee
	Mary F. Miller, Trustee
	Joel W. Motley, Trustee
	Joanne Pace, Trustee
	Joseph M. Wikler, Trustee
	Peter I. Wold, Trustee
	William F. Glavin, Jr., Trustee, President and Principal Executive Officer
	Christopher Proctor, Vice President
	Adam Wilde, Vice President
	Arthur S. Gabinet, Secretary and Chief Legal Officer
	Christina M. Nasta, Vice President and Chief Business Officer
	Mark S. Vandehey, Vice President and Chief Compliance Officer
	Brian W. Wixted, Treasurer and Principal Financial & Accounting Officer
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	Kramer Levin Naftalis & Frankel LLP

© 2014 OppenheimerFunds, Inc. All rights reserved.

37      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

PRIVACY POLICY NOTICE

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

Information Sources

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

• Applications or other forms

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

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

• Your transactions with us, our affiliates or others

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

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

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

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

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

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

Protection of Information

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

Disclosure of Information

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

Right of Refusal

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

38      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Internet Security and Encryption

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

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

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

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

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

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

Other Security Measures

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

How You Can Help

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

Who We Are

This joint notice describes the privacy policies of the Oppenheimer funds, OppenheimerFunds, Inc., and each of its 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 November 2013. In the event it is updated or changed, we will post an updated notice on our website at oppenheimerfunds.com. If you have any questions about these privacy policies, write to us at P.O. Box 5270, Denver, CO 80217-5270, email us by clicking on the Contact Us section of our website at oppenheimerfunds.com or call us at 1.800.CALL OPP (225.5677).

39      OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Item 2. Code of Ethics.

Not applicable to semiannual reports.

Item 3. Audit Committee Financial Expert.

Not applicable to semiannual reports.

Item 4. Principal Accountant Fees and Services.

Not applicable to semiannual reports.

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 11/29/2013, the registrant’s principal executive officer and principal financial officer found the registrant’s disclosure controls and procedures to provide reasonable assurances that information required to be disclosed by the registrant in the reports that it files under the Securities Exchange Act of 1934 (a) is accumulated and communicated to registrant’s management, including its principal executive officer and principal financial officer, to allow timely decisions regarding required disclosure, and (b) is recorded, processed, summarized and reported, within the time periods specified in the rules and forms adopted by the U.S. Securities and Exchange Commission.

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

Item 12. Exhibits.

(a) (1) Not applicable to semiannual reports.

(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 Institutional Money Market Fund

By:	/s/ William F. Glavin, Jr.
	William F. Glavin, Jr.
	Principal Executive Officer
Date:	1/13/2014

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

By:	/s/ William F. Glavin, Jr.
	William F. Glavin, Jr.
	Principal Executive Officer
Date:	1/13/2014

By:	/s/ Brian W. Wixted
	Brian W. Wixted
	Principal Financial Officer
Date:	1/13/2014

EX-99.CERT

Exhibit 99.CERT

Section 302 Certifications

CERTIFICATIONS

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

1. I have reviewed this report on Form N-CSR of Oppenheimer Institutional Money Market Fund;

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

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

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

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

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

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

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

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

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

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

Date: 1/13/2014

/s/ William F. Glavin, Jr.

William F. Glavin, Jr.

Principal Executive Officer

Exhibit 99.CERT

Section 302 Certifications

CERTIFICATIONS

I, Brian W. Wixted, certify that:

1. I have reviewed this report on Form N-CSR of Oppenheimer Institutional Money Market Fund;

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

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

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

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

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

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

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

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

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

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

Date: 1/13/2014

/s/ Brian W. Wixted

Brian W. Wixted

Principal Financial Officer

EX-99.906CERT

EX-99.906CERT

Section 906 Certifications

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

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

William F. Glavin, Jr., Principal Executive Officer, and Brian W. Wixted, Principal Financial Officer, of Oppenheimer Institutional Money Market Fund (the “Registrant”), each certify to the best of his knowledge that:

1. The Registrant’s periodic report on Form N-CSR for the period ended 11/29/2013 (the “Form N-CSR”) fully complies with the requirements of Section 15(d) of the Securities Exchange Act of 1934, as amended; and

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

Principal Executive Officer	Principal Financial Officer
Oppenheimer Institutional Money Market Fund	Oppenheimer Institutional Money Market Fund
/s/ William F. Glavin, Jr.	/s/ Brian W. Wixted
William F. Glavin, Jr.	Brian W. Wixted
Date: 1/13/2014	Date: 1/13/2014