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)

Robert G. Zack, Esq.
OppenheimerFunds, 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: 11/30/2010

Item 1. Reports to Stockholders.

November 30, 2010 Oppenheimer Management Institutional Money Commentary and Market Fund Semiannual Report MANAGEMENT COMMENTARY An Interview with Your Fund’s Portfolio Managers SEMI ANNUAL REPORT Listing of Investments Financial Statements

NOTES

An investment in the Fund is not insured or 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.

Investors should consider the Fund’s investment objectives, risks, expenses and other charges carefully before investing. The Fund’s prospectus and, if available, the Fund’s summary prospectus contain this and other information about the Fund, and may be obtained by asking your financial advisor, calling us at 1.800.525.7048 or visiting our website at www.oppenheimerfunds.com. Read the prospectus and, if available, the summary prospectus carefully before investing.

5 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

FUND EXPENSES

Fund Expenses. As a shareholder of the Fund, you incur 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 30, 2010.

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.

6 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

	Beginning		Ending		Expenses
	Account		Account		Paid During
	Value		Value		6 Months Ended
	June 1, 2010		November 30, 2010		November 30, 2010
Actual
Class E	$	1,000.00	$	1,001.30	$	0.55
Class L		1,000.00		1,001.00		0.80
Class P		1,000.00		1,000.80		1.05
Hypothetical (5% return before expenses)
Class E		1,000.00		1,024.52		0.56
Class L		1,000.00		1,024.27		0.81
Class P		1,000.00		1,024.02		1.07

Expenses are equal to the Fund’s annualized expense ratio for that class, multiplied by the average account value over the period, multiplied by 183/365 (to reflect the one-half year period). Those annualized expense ratios, excluding indirect expenses from affiliated fund, based on the 6-month period ended November 30, 2010 are as follows:

Class	Expense Ratios
Class E		0.11	%
Class L		0.16
Class P		0.21

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

7 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS November 30, 2010 / Unaudited

	Maturity		Final Legal		Principal
	Date*		Maturity Date**		Amount		Value
Certificates of Deposit—26.6%
Yankee Certificates of Deposit—26.6%
Bank of Montreal, Chicago, 0.27%		2/25/11		2/25/11	$	50,000,000	$	50,000,000
Bank of Nova Scotia, Houston TX:
0.24%		1/25/11		1/25/11		75,000,000		74,997,710
0.41%		1/25/11		1/25/11		65,700,000		65,714,018
Barclays Bank plc, New York, 0.439%1		3/5/11		7/19/11		70,000,000		70,000,000
BNP Paribas, New York:
0.30%		12/21/10		12/21/10		100,000,000		100,000,000
0.30%		12/22/10		12/22/10		100,000,000		100,000,000
0.34%		3/29/11		3/29/11		37,000,000		37,000,000
National Australia Bank, New York:
0.26%		12/29/10		12/29/10		101,900,000		101,899,996
0.26%		1/18/11		1/18/11		100,000,000		100,000,000
Nordea Bank Finland plc, New York:
0.27%		3/4/11		3/4/11		50,000,000		50,000,000
0.28%		2/7/11		2/7/11		43,000,000		43,000,000
0.34%		5/24/11		5/24/11		42,000,000		42,000,000
0.68%		12/16/10		12/16/10		50,000,000		50,000,000
0.69%		12/17/10		12/17/10		50,000,000		50,000,000
0.70%		12/10/10		12/10/10		50,000,000		50,000,000
0.71%		12/6/10		12/6/10		47,000,000		47,000,063
Rabobank Nederland NV, 0.286%1		2/12/11		8/12/11		59,000,000		59,000,000
Rabobank Nederland NV, New York:
0.288%1		1/29/11		7/29/11		55,300,000		55,300,000
0.323%1		12/12/10		5/12/11		50,000,000		50,000,000
0.335%		3/16/11		3/16/11		34,000,000		34,005,434
0.353%1		12/25/10		6/27/11		70,000,000		70,000,000
0.42%		11/10/11		11/10/11		50,000,000		50,000,000
0.50%		9/14/11		9/14/11		21,000,000		21,004,996
Royal Bank of Canada, New York:
0.0%1,2		12/2/11		12/2/11		100,000,000		100,000,000
0.38%1		12/1/10		11/10/11		104,500,000		104,500,000
0.40%1		12/1/10		8/16/11		100,000,000		100,000,000
Svenska Handelsbanken, New York:
0.265%		1/24/11		1/24/11		50,000,000		50,000,000
0.27%		2/4/11		2/4/11		50,000,000		50,000,000
0.29%		2/22/11		2/22/11		50,000,000		50,000,000
Westpac Banking Corp., New York, 0.353%1		12/7/10		12/7/10		50,000,000		50,000,000
Total Certificates of Deposit (Cost $1,875,422,217)								1,875,422,217

8 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

	Maturity		Final Legal		Principal
	Date*		Maturity Date**		Amount		Value
Direct Bank Obligations—21.0%
Barclays US Funding LLC:
0.30%		3/1/11		3/1/11	$	100,000,000	$	99,925,000
0.32%		3/2/11		3/2/11		50,000,000		49,959,556
Branch Banking & Trust Co., Grand Cayman, 0.20%		12/1/10		12/1/10		178,000,000		178,000,000
Commonwealth Bank of Australia:
0.255%3		12/7/10		12/7/10		50,000,000		49,997,875
0.27%3		2/24/11		2/24/11		46,000,000		45,970,675
Credit Agricole North America, Inc.:
0.25%		12/9/10		12/9/10		87,000,000		86,995,167
0.26%		12/15/10		12/15/10		100,000,000		99,989,889
ING (US) Funding LLC, 0.24%		12/1/10		12/1/10		279,100,000		279,100,000
Intesa Funding LLC:
0.26%		12/1/10		12/1/10		200,000,000		200,000,000
0.26%		12/7/10		12/7/10		16,000,000		15,999,307
Santander Central Hispano Finance (Delaware), Inc., 0.50%		1/3/11		1/3/11		100,000,000		99,954,167
Societe Generale North America, Inc.:
0.26%		12/6/10		12/6/10		100,000,000		99,996,389
0.27%		12/1/10		12/1/10		26,900,000		26,900,000
0.28%		1/14/11		1/14/11		50,000,000		49,982,889
0.29%		1/18/11		1/18/11		47,000,000		46,981,827
0.29%		1/24/11		1/24/11		46,000,000
								45,979,990
Total Direct Bank Obligations (Cost $1,475,732,731)								1,475,732,731
Short-Term Notes—43.5%
Capital Markets—1.3%
BNP Paribas Finance, Inc.:
0.29%		12/9/10		12/9/10		25,300,000		25,298,370
0.30%		12/17/10		12/17/10		2,500,000		2,499,667
0.39%		3/23/11		3/23/11		61,900,000		61,824,895
								89,622,932
Electric Utilities—1.0%
Electricite De France, 0.25%3		12/10/10		12/10/10		71,600,000		71,595,525
Leasing & Factoring—0.2%
Toyota Motor Credit Corp., 0.28%		12/10/10		12/10/10		13,900,000		13,899,027
Municipal—8.3%
Berks Cnty. Industrial Development Revenue Bonds, Lebanon Valley Mall Project, Series 96B, 0.33%1		12/7/10		12/7/10		3,060,000		3,060,000
Bloomingdale Life Time Fitness LLC Revenue Bonds, Series 2000, 0.37%1		12/7/10		12/7/10		5,850,000		5,850,000

9 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS Unaudited / Continued

	Maturity		Final Legal		Principal
	Date*		Maturity Date**		Amount		Value
Municipal Continued
Capital Markets Access Co. LC Bonds, Carteret Investment Assn. LLC, Series 2008, 0.33%1		12/7/10		12/7/10	$	7,370,000	$	7,370,000
Carenet Health Systems & Service, Inc. Nts., Series 1999, 0.70%1		12/7/10		12/7/10		4,350,000		4,350,000
Charlotte, NC Certificates of Participation, NASCAR Hall of Fame Facilities, Series 09D, 0.32%1		12/7/10		12/7/10		25,000,000		25,000,000
Cleveland, OH Airport System Revenue Bonds, Series 2008F, 0.26%1		12/7/10		12/7/10		30,000,000		30,000,000
Cobb Cnty., GA Development Authority Revenue Bonds, Presbyterian Village-Austell, Inc., 0.35%1		12/7/10		12/7/10		3,005,000		3,005,000
Cobb Cnty., GA Hospital Authority Revenue Anticipation Certificates, Equipment Pool Project, Series 2004, 0.30%1		12/7/10		12/7/10		25,000,000		25,000,000
District of Columbia Multimodal University Revenue Bonds, American University Issue, Series 2006A, 0.32%1		12/7/10		12/7/10		17,000,000		17,000,000
Easton, MD Bonds, William Hill Manor Facility, Series 2009B, 0.35%1		12/7/10		12/7/10		4,145,000		4,145,000
Everett Clinic (The) Bonds, Series 2002, 0.37%1		12/7/10		12/7/10		10,600,000		10,600,000
Great Falls Clinic LLP Bonds, Series 06, 0.37%1		12/7/10		12/7/10		18,010,000		18,010,000
Henrico Cnty., VA Economic Development Authority Revenue Bonds, Bon Secours Health System, Inc., Series 08B, 0.28%1		12/7/10		12/7/10		20,370,000		20,370,000
IN Development Finance Authority Education Facilities Bonds, Indianapolis Museum of Art, Series 2004, 0.30%1		12/7/10		12/7/10		43,300,000		43,300,000
Johnson, TN Health & Education Facilities, Mountain States Health:
Series 2007B-1, 0.34%1		12/7/10		12/7/10		20,650,000		20,650,000
Series 2007B-2, 0.28%1		12/7/10		12/7/10		18,250,000		18,250,000
Macon-Bibb Cnty. Industrial Development Authority Revenue Bonds, Bass Pro Outdoor World, Series 2005, 0.40%1		12/7/10		12/7/10		21,000,000		21,000,000
Metro Atlanta Rapid Transit Authority, GA Sales Tax Revenue Bonds, Series 2000A, 0.26%1		12/7/10		12/7/10		25,000,000		25,000,000
Nassau Health Care Corp. Bonds, Series 2009A, 0.34%1		12/7/10		12/7/10		11,500,000		11,500,000
Newport News, VA Economic Development Bonds, Newport News Shipbuilding Project, 0.33%1		12/7/10		12/7/10		3,520,000		3,520,000

10 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

	Maturity		Final Legal		Principal
	Date*		Maturity Date**		Amount		Value
Municipal Continued
NY Dormitory Authority Revenue Bonds, St. John’s University, Series 2008B-2, 0.32%1		12/7/10		12/7/10	$	19,110,000	$	19,110,000
OH Higher Education Facilities Commission, Xavier University 2008 Project, Series B, 0.31%1		12/7/10		12/7/10		20,480,000		20,480,000
Private Colleges & Universities Authority Revenue Bonds, Mercer University Project, Series 2006B, 0.26%1		12/7/10		12/7/10		6,315,000		6,315,000
Russell Cnty., VA Industrial Development Authority Hospital Bonds, Mountain States Health Alliance, Series 08B, 0.33%1		12/7/10		12/7/10		10,775,000		10,775,000
San Bernardino Cnty., CA Certificates of Participation, Series 2008A, 0.32%1		12/7/10		12/7/10		23,450,000		23,450,000
SC Jobs-Economic Development Authority Bonds, South Atlantic Canners, Inc., Series 2001, 0.47%1		12/7/10		12/7/10		5,000,000		5,000,000
St. Paul, MN Bonds, River Center Arena Project, Series 2009A, 0.28%1		12/7/10		12/7/10		17,900,000		17,900,000
St. Paul, MN Port Authority Revenue Refunding Bonds, Series 2009-12EE, 0.33%1		12/7/10		12/7/10		1,150,000		1,150,000
Tallahassee Orthopedic Center LC Bonds, Series 2004, 0.32%1		12/7/10		12/7/10		4,535,000		4,535,000
Tift Cnty. Development Authority Industrial Development Revenue Bonds, Heatcraft Refrigeration Products, Series 2008B, 0.28%1		12/7/10		12/7/10		6,700,000		6,700,000
Trinitas Hospital Bonds, Series 2006, 0.28%1		12/7/10		12/7/10		14,045,000		14,045,000
Tuscaloosa Cnty., AL Industrial Development Authority, Gulf Opportunity Zone Hunt Refining Project, Series 2009, 0.32%1		12/7/10		12/7/10		30,000,000		30,000,000
TX Veterans’ Housing Assistance Program Fund I:
Series 05C, 0.26%1		12/7/10		12/7/10		7,645,000		7,645,000
Series 09C, 0.26%1		12/7/10		12/7/10		11,700,000		11,700,000
TX Veterans’ Land Board Fund II:
Series 2000, 0.30%1		12/7/10		12/7/10		39,655,000		39,655,000
Series 2000A, 0.30%1		12/7/10		12/7/10		16,855,000		16,855,000
WA Economic Development Finance Authority Industrial Development Revenue Bonds, Canam Steel Corp. Project, Series 2000D, 0.61%1		12/7/10		12/7/10		3,700,000		3,700,000
WA Health Care Facilities Authority, MultiCare Health System, Series 2009A, 0.32%1		12/7/10		12/7/10		25,500,000		25,500,000
Winston-Salem, NC Certificates of Participation, Series 1992, 0.33%1		12/7/10		12/7/10		6,250,000		6,250,000
								587,745,000

11 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS Unaudited / Continued

	Maturity		Final Legal		Principal
	Date*		Maturity Date**		Amount		Value
Oil, Gas & Consumable Fuels—1.4%
Total Capital Canada, 0.47%3		1/19/11		1/19/11	$	99,000,000	$	98,935,987
Personal Products—2.8%
Reckitt Benckiser Treasury Services plc:
0.27%3		1/6/11		1/6/11		50,000,000		49,986,500
0.28%3		1/7/11		1/7/11		50,000,000		49,985,611
0.28%3		1/14/11		1/14/11		99,000,000		98,966,120
								198,938,231
Receivables Finance—16.0%
Alpine Securitization Corp., 0.25%		12/10/10		12/10/10		38,904,000		38,901,569
Barton Capital Corp.:
0.25%3		12/8/10		12/8/10		35,000,000		34,998,299
0.26%3		12/1/10		12/1/10		30,009,000		30,009,000
Fairway Finance Corp.:
0.255%3		12/3/10		12/3/10		33,964,000		33,963,519
0.27%3		2/2/11		2/2/11		40,034,000		40,015,084
Falcon Asset Securitization Co. LLC:
0.25%3		12/15/10		12/15/10		113,776,000		113,764,938
0.27%3		1/24/11		1/24/11		24,700,000		24,689,997
0.27%3		2/2/11		2/2/11		10,000,000		9,995,275
0.27%3		2/4/11		2/4/11		50,000,000		49,975,625
Gemini Securitization Corp., 0.25%3		12/9/10		12/9/10		23,400,000		23,398,700
Jupiter Securitization Co. LLC:
0.25%3		12/14/10		12/14/10		15,850,000		15,848,569
0.27%3		2/3/11		2/3/11		50,000,000		49,976,000
0.27%3		2/23/11		2/23/11		50,000,000		49,968,500
Lexington Parker Capital Co. LLC, 0.40%3		12/2/10		12/2/10		100,000,000		99,998,889
Market Street Funding LLC, 0.265%3		12/22/10		12/22/10		59,304,000		59,294,833
Mont Blanc Capital Corp., 0.27%3		12/14/10		12/14/10		50,000,000		49,995,125
Old Line Funding Corp.:
0.26%3		12/20/10		12/20/10		45,629,000		45,622,739
0.27%3		12/7/10		12/7/10		23,866,000		23,864,926
0.28%3		1/4/11		1/4/11		30,027,000		30,019,060
0.28%3		1/7/11		1/7/11		51,373,000		51,358,216
0.28%3		1/18/11		1/18/11		40,000,000		39,985,067
Thunder Bay Funding LLC:
0.25%3		12/1/10		12/1/10		50,041,000		50,041,000
0.27%3		2/1/11		2/1/11		50,000,000		49,976,750
0.27%3		2/7/11		2/7/11		50,000,000		49,974,500
0.28%3		1/18/11		1/18/11		56,248,000		56,227,001
								1,121,863,181

12 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

	Maturity		Final Legal		Principal
	Date*		Maturity Date**		Amount		Value
Special Purpose Financial—9.2%
Crown Point Capital Co.:
0.40%		12/3/10		12/3/10	$	50,000,000	$	49,998,889
0.40%		12/7/10		12/7/10		13,400,000		13,399,107
0.40%		12/10/10		12/10/10		20,000,000		19,998,000
0.40%		1/4/11		1/4/11		50,000,000		49,981,111
0.40%		1/5/11		1/5/11		23,100,000		23,091,017
0.40%		1/12/11		1/12/11		50,000,000		49,976,667
FCAR Owner Trust I:
0.28%		12/23/10		12/23/10		55,400,000		55,389,989
0.30%		1/10/11		1/10/11		11,500,000		11,496,167
0.30%		1/13/11		1/13/11		91,600,000		91,567,177
0.31%		2/4/11		2/4/11		50,000,000		49,972,014
Lexington Parker Capital Co. LLC:
0.40%3		12/3/10		12/3/10		57,700,000		57,698,718
0.40%3		12/6/10		12/6/10		59,600,000		59,596,689
0.40%3		12/8/10		12/8/10		100,000,000		99,992,222
0.40%3		12/9/10		12/9/10		9,100,000		9,099,191
0.40%3		1/5/11		1/5/11		12,000,000		11,995,333
								653,252,291
U.S. Government Obligations—3.3%
Straight-A Funding LLC, Series I:
0.26%3		1/24/11		1/24/11		50,000,000		49,980,500
0.26%3		1/26/11		1/26/11		50,000,000		49,979,778
0.26%3		2/2/11		2/2/11		131,487,000		131,427,173
								231,387,451
Total Short-Term Notes (Cost $3,067,239,625)								3,067,239,625
U.S. Government Obligations—3.8%
U.S. Treasury Nts.:
0.875%		2/28/11		2/28/11		72,200,000		72,289,510
0.875%		3/31/11		3/31/11		49,000,000		49,070,328
0.875%		4/30/11		4/30/11		31,000,000		31,043,368
1.125%		12/15/11		12/15/11		50,000,000		50,402,986
4.875%		7/31/11		7/31/11		31,000,000		31,920,124
5.125%		6/30/11		6/30/11		31,000,000		31,840,375
Total U.S. Government Obligations (Cost $266,566,691)								266,566,691

13 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF INVESTMENTS Unaudited / Continued

	Maturity		Final Legal		Principal
	Date*		Maturity Date**		Amount			Value
U.S. Government Agencies—3.4%
Federal Home Loan Bank:
0.40%		11/28/11		11/28/11	$	50,000,000		$	50,000,000
0.40%		11/28/11		11/28/11		90,000,000			90,000,000
0.45%4		12/16/11		12/16/11		50,000,000			50,000,000
0.50%4		12/28/11		12/28/11		50,000,000			50,000,000
Total U.S. Government Agencies (Cost $240,000,000)									240,000,000
					Shares
Investment Company—4.5%
Prime Money Market Fund RBC Institutional, Cl. 1, 0.18%5 (Cost $314,540,658)		12/1/10		12/1/10		314,540,658			314,540,658
Total Investments, at Value (Cost $7,239,501,922)						102.8	%		7,239,501,922
Liabilities in Excess of Other Assets						(2.8	)		(198,013,991	)
Net Assets						100.0	%	$	7,041,487,931

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.

*	The Maturity Date represents the date used to calculate the Fund’s weighted average maturity as determined under Rule  2a-7.
**	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.
1.	Represents the current interest rate for a variable or increasing rate security.
2.	Interest rate is less than 0.0005%.
3.	Security issued in an exempt transaction without registration under the Securities Act of 1933. Such securities amount to $2,018,169,509 or 28.66% of the Fund’s net assets, and have been determined to be liquid pursuant to guidelines adopted by the Board of Trustees.
4.	When-issued security or delayed delivery to be delivered and settled after November 30, 2010. See Note 1 of the accompanying Notes.
5.	Rate shown is the 7-day yield as of November 30, 2010.

Valuation Inputs

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 (such as unadjusted quoted prices for similar assets and market corroborated inputs such as interest rates, prepayment speeds, credit risks, etc.)

14 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

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

The table below categorizes amounts that are included in the Fund’s Statement of Assets and Liabilities as of November 30, 2010 based on valuation input level:

					Level 3 –
	Level 1 –		Level 2 –		Significant
	Unadjusted		Other Significant		Unobservable
	Quoted Prices		Observable Inputs		Inputs		Value
Assets Table
Investments, at Value:
Certificates of Deposit	$	—	$	1,825,422,217	$	—	$	1,825,422,217
Direct Bank Obligations		—		1,525,732,731		—		1,525,732,731
Short-Term Notes		—		3,067,239,625		—		3,067,239,625
U.S. Government Obligations		—		266,566,691		—		266,566,691
U.S. Government Agencies		—		240,000,000		—		240,000,000
Investment Company		314,540,658		—		—		314,540,658
Total Assets	$	314,540,658	$	6,924,961,264	$	—	$	7,239,501,922

Currency contracts and forwards, if any, are reported at their unrealized appreciation/depreciation at measurement date, which represents the change in the contract’s value from trade date. Futures, if any, are reported at their variation margin at measurement date, which represents the amount due to/from the Fund at that date. All additional assets and liabilities included in the above table are reported at their market value at measurement date.

See the accompanying Notes for further discussion of the methods used in determining value of the Fund’s investments, and a summary of changes to the valuation methodologies, if any, during the reporting period.

See accompanying Notes to Financial Statements.

15 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF ASSETS AND LIABILITIES Unaudited

November 30, 2010
Assets
Investments, at value (cost $7,239,501,922)—see accompanying statement of investments	$	7,239,501,922
Receivables and other assets:
Interest and dividends		3,160,066
Shares of beneficial interest sold		445,001
Other		213,228
Total assets		7,243,320,217
Liabilities
Bank overdraft		65,572
Payables and other liabilities:
Investments purchased (including $100,000,000 purchased on a when-issued or delayed delivery basis)		200,000,000
Dividends		1,014,167
Trustees’ compensation		577,691
Transfer and shareholder servicing agent fees		47,502
Shareholder communications		12,366
Distribution and service plan fees		628
Other		114,360
Total liabilities		201,832,286
Net Assets	$	7,041,487,931
Composition of Net Assets
Par value of shares of beneficial interest	$	7,041,786
Additional paid-in capital		7,034,743,987
Accumulated net investment loss		(351,222	)
Accumulated net realized gain on investments		53,380
Net Assets	$	7,041,487,931
Net Asset Value Per Share
Class E:
Net asset value and redemption price per share (based on net assets of $5,923,685,955 and 5,923,897,534 shares of beneficial interest outstanding)	$	1.00
Class L Shares:
Net asset value and redemption price per share (based on net assets of $1,109,347,632 and 1,109,449,156 shares of beneficial interest outstanding)	$	1.00
Class P Shares:
Net asset value and redemption price per share (based on net assets of $8,454,344 and 8,439,083 shares of beneficial interest)	$	1.00

See accompanying Notes to Financial Statements.

16 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENT OF OPERATIONS Unaudited

For the Six Months Ended November 30, 2010
Investment Income
Interest	$	11,623,304
Dividends		292,466
Total investment income		11,915,770
Expenses
Management fees		3,330,922
Transfer and shareholder servicing agent fees:
Class L		277,272
Class P		2,209
Shareholder communications:
Class E		9,571
Class L		47,822
Trustees’ compensation		63,606
Custodian fees and expenses		17,437
Service plan fees—Class P		11,047
Administration service fees		750
Other		124,933
Total expenses		3,885,569
Less waivers and reimbursements of expenses		(8,837	)
Net expenses		3,876,732
Net Investment Income		8,039,038
Net Realized Gain on Investments		26,560
Net Increase in Net Assets Resulting from Operations	$	8,065,598

See accompanying Notes to Financial Statements.

17 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

STATEMENTS OF CHANGES IN NET ASSETS Unaudited

	Six Months			Year
	Ended			Ended
	November 30, 2010			May 31,
	(Unaudited)			2010
Operations
Net investment income	$	8,039,038		$	20,132,265
Net realized gain		26,560			26,820
Net increase in net assets resulting from operations		8,065,598			20,159,085
Dividends and/or Distributions to Shareholders
Dividends from net investment income:
Class E		(7,236,709	)		(16,345,031	)
Class L		(1,146,340	)		(4,247,043	)
Class P		(7,217	)		(24,432	)
		(8,390,266	)		(20,616,506	)
Beneficial Interest Transactions
Net increase (decrease) in net assets resulting from beneficial interest transactions:
Class E		638,831,740			(1,322,941,031	)
Class L		345,575,055			(694,033,545	)
Class P		202,848			(9,570,524	)
		984,609,643			(2,026,545,100	)
Net Assets
Total increase (decrease)		984,284,975			(2,027,002,521	)
Beginning of period		6,057,202,956			8,084,205,477
End of period (including accumulated net investment income (loss) of $(351,222) and $6, respectively)	$	7,041,487,931		$	6,057,202,956

See accompanying Notes to Financial Statements.

18 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

FINANCIAL HIGHLIGHTS Unaudited

	Six Months
	Ended
	November 30, 2010									Year Ended May 31,
Class E	(Unaudited)			2010			2009			2008			20071
Per Share Operating Data
Net asset value, beginning of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Income from investment operations—net investment income and net realized gain2		—	3		—	3		.02			.05			.03
Dividends and/or distributions to shareholders:
Dividends from net investment income		—	3		—	3		(.02	)		(.05	)		(.03	)
Distributions from net realized gain		—			—			—	3		—			—
Total dividends and/or distributions to shareholders		—			—			(.02	)		(.05	)		(.03	)
Net asset value, end of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Total Return4		0.13	%		0.28	%		1.96	%		4.69	%		3.52	%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	5,923,686		$	5,285,125		$	6,608,401		$	5,697,092		$	3,963,198
Average net assets (in thousands)	$	5,532,353		$	5,755,335		$	5,649,134		$	5,462,546		$	3,623,302
Ratios to average net assets:5
Net investment income		0.25	%		0.28	%		1.89	%		4.55	%		5.25	%
Total expenses		0.11	%		0.12	%		0.13	%		0.11	%		0.11	%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.11	%		0.12	%		0.13	%		0.11	%		0.11	%

1.	For the period from October 3, 2006 (commencement of operations) to May 31, 2007.
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 Unaudited / Continued

	Six Months
	Ended
	November 30, 2010									Year Ended May 31,
Class L	(Unaudited)			2010			2009			2008			20071
Per Share Operating Data
Net asset value, beginning of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Income from investment operations—net investment income and net realized gain2		—	3		—	3		.02			.05			.04
Dividends and/or distributions to shareholders:
Dividends from net investment income		—	3		—	3		(.02	)		(.05	)		(.04	)
Distributions from net realized gain		—			—			—	3		—			—
Total dividends and/or distributions to shareholders		—			—			(.02	)		(.05	)		(.04	)
Net asset value, end of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Total Return4		0.10	%		0.23	%		1.95	%		4.69	%		3.61	%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	1,109,348		$	763,826		$	1,457,981		$	753,342		$	502
Average net assets (in thousands)	$	1,107,917		$	1,766,105		$	1,219,384		$	443,323		$	68
Ratios to average net assets:5
Net investment income		0.20	%		0.23	%		1.97	%		3.93	%		3.62	%
Total expenses		0.16	%		0.17	%		0.15	%		0.12	%		0.08	%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.16	%		0.17	%		0.14	%		0.12	%		0.08	%

1.	For the period from October 3, 2006 (commencement of operations) to May 31, 2007.
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

	Six Months
	Ended
	November 30, 2010									Year Ended May 31,
Class P	(Unaudited)			2010			2009			2008			20071
Per Share Operating Data
Net asset value, beginning of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Income from investment operations—net investment income and net realized gain2		—	3		—	3		.02			.05			—	3
Dividends and/or distributions to shareholders:
Dividends from net investment income		—	3		—	3		(.02	)		(.05	)		—	3
Distributions from net realized gain		—			—			—	3		—			—
Total dividends and/or distributions to shareholders		—			—			(.02	)		(.05	)		—
Net asset value, end of period	$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Total Return4		0.08	%		0.18	%		1.88	%		4.68	%		0.15	%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	8,454		$	8,252		$	17,823		$	939		$	10
Average net assets (in thousands)	$	8,814		$	12,254		$	139,489		$	517		$	10
Ratios to average net assets:5
Net investment income		0.15	%		0.19	%		2.26	%		3.78	%		4.79	%
Total expenses		0.41	%		0.53	%		0.39	%		2.14	%		0.10	%
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.21	%		0.22	%		0.18	%		0.20	%		0.10	%

1.	For the period from May 21, 2007 (inception of offering) to May 31, 2007.
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 STATEMENTS Unaudited

1. Significant Accounting Policies

Oppenheimer Institutional Money Market Fund (the “Fund”) is registered under the Investment Company Act of 1940, as amended, as an open-end management investment company. The Fund’s investment objective is to seek current income and stability of principal. The Fund’s investment adviser is OppenheimerFunds, Inc. (the “Manager”). As of November 30, 2010, approximately 80% of the shares of the Fund were owned by 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 distribution and 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.

Securities Valuation. 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.

     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. Unadjusted quoted prices in active markets for identical securities are classified as “Level 1,” inputs other than unadjusted quoted prices for an asset that are observable are classified as “Level 2” and significant unobservable inputs, including the Manager’s judgment about the assumptions that a market participant would use in pricing an asset or liability, are classified as “Level 3.” The inputs used for valuing securities are not necessarily an indication of the risks associated with investing in those securities. A table summarizing the Fund’s investments under these levels of classification is included following the Statement of Investments.

     In the absence of a readily available unadjusted quoted market price, including for securities whose values have been materially affected by what the Manager identifies as a significant event occurring before the Fund’s assets are valued but after the close of the securities’ respective exchanges, the Manager, acting through its internal valuation committee, in good faith determines the fair valuation of that asset using consistently applied procedures under the supervision of the Board of Trustees (which reviews those fair valuations by the Manager). Those procedures include certain standardized methodologies to

22 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

fair value securities. Such methodologies include, but are not limited to, pricing securities 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 adjusted for any discounts related to 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.

     There have been no significant changes to the fair valuation methodologies of the Fund during the period.

Securities on a When-Issued or Delayed Delivery Basis. The Fund may purchase securities on a “when-issued” basis, and may purchase or sell securities on a “delayed delivery” basis. “When-issued” or “delayed delivery” refers to securities whose terms and indenture are available and for which a market exists, but which are not available for immediate delivery. Delivery and payment for securities that have been purchased by the Fund on a when-issued basis normally takes place within six months and possibly as long as two years or more after the trade date. During this period, such securities do not earn interest, are subject to market fluctuation and may increase or decrease in value prior to their delivery. The purchase of securities on a when-issued basis may increase the volatility of the Fund’s net asset value to the extent the Fund executes such transactions while remaining substantially fully invested. When the Fund engages in when-issued or delayed delivery transactions, it relies on the buyer or seller, as the case may be, to complete the transaction. Their failure to do so may cause the Fund to lose the opportunity to obtain or dispose of the security at a price and yield it considers advantageous. The Fund may also sell securities that it purchased on a when-issued basis or forward commitment prior to settlement of the original purchase.

As of November 30, 2010, the Fund had purchased securities issued on a when-issued or delayed delivery basis as follows:

	When-Issued or Delayed
	Delivery Basis Transactions
Purchased securities	$	100,000,000

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.

23 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

NOTES TO FINANCIAL STATEMENTS Unaudited / Continued

1. Significant Accounting Policies Continued

     During the fiscal year ended May 28, 2010, the Fund did not utilize any capital loss carryforward to offset capital gains realized in that fiscal year.

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 30, 2010, the Fund’s projected benefit obligations, payments to retired trustees and accumulated liability were as follows:

Projected Benefit Obligations Increased	$	—
Payments Made to Retired Trustees		—
Accumulated Liability as of November 30, 2010		354,099

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.

24 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

Custodian Fees. “Custodian fees and expenses” in the Statement of Operations may include interest expense incurred by the Fund on any cash overdrafts of its custodian account during the period. Such cash overdrafts may result from the effects of failed trades in portfolio securities and from cash outflows resulting from unanticipated shareholder redemption activity. The Fund pays interest to its custodian on such cash 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. 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 November 30, 2010						Year Ended May 31, 2010
	Shares			Amount			Shares			Amount
Class E
Sold		21,217,974,519		$	21,217,974,519			42,968,072,418		$	42,968,072,418
Dividends and/or distributions reinvested		882,766			882,766			1,979,106			1,979,106
Redeemed		(20,580,025,545	)		(20,580,025,545	)		(44,292,992,555	)		(44,292,992,555	)
Net increase (decrease)		638,831,740		$	638,831,740			(1,322,941,031	)	$	(1,322,941,031	)
Class L
Sold		11,567,767,339		$	11,567,767,339			10,394,461,328		$	10,394,461,328
Dividends and/or distributions reinvested		681,519			681,519			2,671,518			2,671,518
Redeemed		(11,222,873,803	)		(11,222,873,803	)		(11,091,166,391	)		(11,091,166,391	)
Net increase (decrease)		345,575,055		$	345,575,055			(694,033,545	)	$	(694,033,545	)

25 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

NOTES TO FINANCIAL STATEMENTS Unaudited / Continued

2. Shares of Beneficial Interest Continued

	Six Months Ended November 30, 2010						Year Ended May 31, 2010
	Shares			Amount			Shares			Amount
Class P
Sold		2,000,000		$	2,000,000			35,546,000		$	35,546,000
Dividends and/or distributions reinvested		1,345			1,345			9,266			9,266
Redeemed		(1,798,497	)		(1,798,497	)		(45,125,790	)		(45,125,790	)
Net increase (decrease)		202,848		$	202,848			(9,570,524	)	$	(9,570,524	)

3. 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%.

Transfer Agent Fees. OppenheimerFunds Services (“OFS”), a division of the Manager, acts as the transfer and shareholder servicing agent for the Fund. For the six months ended November 30, 2010, the Fund Paid $262,288 to OFS for services to the Fund.

Administration Service Fees. The Fund pays the Manager a fee of $1,500 per year for preparing and filing the Fund’s tax returns.

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 agreed to waive its management fee and/or reimburse expenses such that “Expenses after waivers, payments and/or reimbursements and reduction to custodian expenses” will not exceed 0.15% for Class E shares, 0.19% for Class L shares and 0.24% for Class P shares.

     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.

     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 30, 2010, the Distributor waived $8,837 for Class P shares.

26 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

     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.

4. Pending Litigation

Since 2009, a number of lawsuits have been filed in federal courts against the Manager, the Distributor, and certain mutual funds (“Defendant Funds”) advised by the Manager and distributed by the Distributor (but not including the Fund). The lawsuits naming the Defendant Funds also name as defendants certain officers, trustees and former trustees of the respective Defendant Funds. The plaintiffs seek class action status on behalf of purchasers of shares of the respective Defendant Fund during a particular time period. The lawsuits raise claims under federal securities laws alleging that, among other things, the disclosure documents of the respective Defendant Fund contained misrepresentations and omissions, that such Defendant Fund’s investment policies were not followed, and that such Defendant Fund and the other defendants violated federal securities laws and regulations. The plaintiffs seek unspecified damages, equitable relief and an award of attorneys’ fees and litigation expenses.

     In 2009, what are claimed to be derivative lawsuits were filed in state court against the Manager and a subsidiary (but not against the Fund), on behalf of the New Mexico Education Plan Trust. These lawsuits allege breach of contract, breach of fiduciary duty, negligence and violation of state securities laws, and seek compensatory damages, equitable relief and an award of attorneys’ fees and litigation expenses.

     Other lawsuits have been filed since 2008 in various state and federal courts, against the Manager and certain of its affiliates. Those lawsuits were filed by investors who made investments through an affiliate of the Manager, and relate to the alleged investment fraud perpetrated by Bernard Madoff and his firm (“Madoff ”). Those suits allege 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 an award of attorneys’ fees and litigation expenses. None of the suits have named the Distributor, any of the Oppenheimer mutual funds or any of their independent Trustees or Directors as defendants. None of the Oppenheimer funds invested in any funds or accounts managed by Madoff.

     The Manager believes that the lawsuits described above are without legal merit and is defending against them vigorously. The Defendant Funds’ Boards of Trustees have also engaged counsel to defend the suits brought against those Funds and the present and former Independent Trustees named in those suits. 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, the Manager believes that these suits should not impair the ability of the Manager 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 funds.

27 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

BOARD APPROVAL OF THE FUND’S INVESTMENT ADVISORY AGREEMENT Unaudited

Each year, the Board of Trustees (the “Board”), including a majority of the independent Trustees, is required to determine whether to renew the Fund’s investment advisory agreement (the “Agreement”). The Investment Company Act of 1940, as amended, requires that the Board request and evaluate, and that the Manager provide, such information as may be reasonably necessary to evaluate the terms of the Agreement. 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, the Board receives information throughout the year regarding Fund services, fees, expenses and performance.

     The Manager and the independent consultant provided information to the Board on the following factors: (i) the nature, quality and extent of the Manager’s services, (ii) the investment performance of the Fund and the Manager, (iii) the fees and expenses of the Fund, including comparative expense information, (iv) the profitability of the Manager and its 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 Manager from its relationship with the Fund. The Board was aware that there are alternatives to retaining the Manager.

     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 Manager’s key personnel who provide such services. The Manager’s duties include providing the Fund with the services of the portfolio managers and the Manager’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. The Manager is 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 Manager also provides the Fund with office space, facilities and equipment.

28 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

     The Board also considered the quality of the services provided and the quality of the Manager’s resources that are available to the Fund. The Board took account of the fact that the Manager has had over fifty years of experience as an investment adviser and that its assets under management rank it among the top mutual fund managers in the United States. The Board evaluated the Manager’s advisory, administrative, accounting, legal and compliance services, and information the Board has received regarding the experience and professional qualifications of the Manager’s 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 Carol Wolf and effective May 2010, Christopher Proctor, the portfolio managers for the Fund, and the Manager’s investment team and analysts. The Board members also considered the totality of their experiences with the Manager as directors or trustees of the Fund and other funds advised by the Manager. The Board considered information regarding the quality of services provided by affiliates of the Manager, 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 Manager’s experience, reputation, personnel, operations and resources, that the Fund benefits from the services provided under the Agreement.

     Investment Performance of the Manager and the Fund. Throughout the year, the Manager provided information on the investment performance of the Fund and the Manager, including comparative performance information. The Board also reviewed information, prepared by the Manager and by the independent consultant, comparing the Fund’s historical performance to relevant market indices and to the performance of other institutional money market funds. The Board noted that the Fund’s one-year and three-year performance was better than its peer group median.

     Costs of Services by the Manager. The Board reviewed the fees paid to the Manager 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 Manager. The independent consultant provided comparative data in regard to the fees and expenses of the Fund and other institutional money market funds with comparable asset levels and distribution features. The Board noted that the Manager has agreed to waive its management fee and/or reimburse expenses such that “Expenses after waivers, payments and/or reimbursements and reduction to custodian expenses” will not exceed 0.15% for Class E shares, 0.19% for Class L shares and 0.24% for Class P shares. 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

29 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

BOARD APPROVAL OF THE FUND’S INVESTMENT ADVISORY AGREEMENT Unaudited / Continued

the Fund will maintain a positive yield. These undertakings are voluntary and may be amended or withdrawn at any time. The Board noted that the Fund’s actual and contractual management fees and total expenses were lower than its peer group median and average.

     Economies of Scale. The Board considered information regarding the Manager’s costs in serving as the Fund’s investment adviser, including the costs associated with the personnel and systems necessary to manage the Fund, and information regarding the Manager’s profitability from its relationship with the Fund. The Board reviewed whether the Manager may realize economies of scale in managing and supporting the Fund, 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 Manager. In addition to considering the profits realized by the Manager, the Board considered information that was provided regarding the direct and indirect benefits the Manager receives as a result of its relationship with the Fund, including compensation paid to the Manager’s affiliates. The Board also considered that the Manager 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 Manager 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 Agreement through September 30, 2011. In arriving at this decision, the Board did not single out 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 Agreement, including the management fee, in light of all of the surrounding circumstances.

30 | 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 1.800.525.7048, (ii) on the Fund’s website at www.oppenheimerfunds.com, and (iii) on the SEC’s website at www.sec.gov. In addition, the Fund is required to file Form N-PX, with its complete proxy voting record for the 12 months ended June 30th, no later than August 31st of each year. The Fund’s voting record is available (i) without charge, upon request, by calling the Fund toll-free at 1.800.525.7048, 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.

31 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

INSTITUTIONAL MONEY MARKET FUND, INC.

Trustees and Officers	Brian F. Wruble, Chairman of the Board of Trustees and Trustee
	David K. Downes, Trustee
	Matthew P. Fink, Trustee
	Phillip A. Griffiths, Trustee
	Mary F. Miller, Trustee
	Joel W. Motley, Trustee
	Mary Ann Tynan, Trustee
	Joseph M. Wikler, Trustee
	Peter I. Wold, Trustee
	William F. Glavin, Jr., Trustee, President and Principal Executive Officer
	Carol E. Wolf, Vice President and Portfolio Manager
	Christopher Proctor, Vice President and Portfolio Manager
	Thomas W. Keffer, Vice President and Chief Business Officer
	Mark S. Vandehey, Vice President and Chief Compliance Officer
	Brian W. Wixted, Treasurer and Principal Financial & Accounting Officer
	Robert G. Zack, Secretary
Manager	OppenheimerFunds, Inc.
Distributor	OppenheimerFunds Distributor, Inc.
Transfer and Shareholder Servicing Agent	OppenheimerFunds Services
Independent Registered Public Accounting Firm	KPMG llp
Legal Counsel	Kramer Levin Naftalis & Frankel LLP
	The financial statements included herein have been taken from the records of the Fund without examination of those records by the independent registered public accounting firm.

©2011 OppenheimerFunds, Inc. All rights reserved.

32 | 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 www.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.

33 | OPPENHEIMER INSTITUTIONAL MONEY MARKET FUND

PRIVACY POLICY NOTICE

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 Distributor, Inc., the trustee of OppenheimerFunds Individual Retirement Accounts (IRAs) and the custodian of the OppenheimerFunds 403(b)(7) tax sheltered custodial accounts. It applies to all Oppenheimer fund accounts you presently have, or may open in the future, using your Social Security number—whether or not you remain a shareholder of our funds. This notice was last updated January 16, 2004. In the event it is updated or changed, we will post an updated notice on our website at www.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 www.oppenheimerfunds.com or call us at 1.800.525.7048.

34 | 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

1.	The Fund’s Governance Committee (the “Committee”) will evaluate potential Board candidates to assess their qualifications. The Committee shall have the authority, upon approval of the Board, to retain an executive search firm to assist in this effort. The Committee may consider recommendations by business and personal contacts of current Board members and by executive search firms which the Committee may engage from time to time and may also consider shareholder recommendations. The Committee may consider the advice and recommendation of the Funds’ investment manager and its affiliates in making the selection.
2.	The Committee shall screen candidates for Board membership. The Committee has not established specific qualifications that it believes must be met by a trustee nominee. In evaluating trustee nominees, the Committee considers, among other things, an individual’s background, skills, and experience; whether the individual is an “interested person” as defined in the Investment Company Act of 1940; and whether the individual would be deemed an “audit committee financial expert” within the meaning of applicable SEC rules. The Committee also considers whether the individual’s background, skills, and experience will complement the background, skills, and experience of other nominees and will contribute to the Board. There are no differences in the manner in which the Committee evaluates nominees for trustees based on whether the nominee is recommended by a shareholder.
3.	The Committee may consider nominations from shareholders for the Board at such times as the Committee meets to consider new nominees for the Board. The Committee shall have the sole discretion to determine the candidates to present to the Board and, in such cases where required, to shareholders. Recommendations for trustee nominees should, at a minimum, be accompanied by the following:

• the name, address, and business, educational, and/or other pertinent background of the person being recommended;

• a statement concerning whether the person is an “interested person” as defined in the Investment Company Act of 1940;

• any other information that the Funds would be required to include in a proxy statement concerning the person if he or she was nominated; and

• the name and address of the person submitting the recommendation and, if that person is a shareholder, the period for which that person held Fund shares.

	The recommendation also can include any additional information which the person submitting it believes would assist the Committee in evaluating the recommendation.
4.	Shareholders should note that a person who owns securities issued by Massachusetts Mutual Life Insurance Company (the parent company of the Funds’ investment adviser) would be deemed an “interested person” under the Investment Company Act of 1940. In addition, certain other relationships with Massachusetts Mutual Life

Insurance Company or its subsidiaries, with registered broker-dealers, or with the Funds’ outside legal counsel may cause a person to be deemed an “interested person.”

5.

Before the Committee decides to nominate an individual as a trustee, Committee members and other directors customarily interview the individual in person. In addition, the individual customarily is asked to complete a detailed questionnaire which is designed to elicit information which must be disclosed under SEC and stock exchange rules and to determine whether the individual is subject to any statutory disqualification from serving as a trustee of a registered investment company.

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 11/30/2010, 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: 01/11/2011

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: 01/11/2011

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

Date: 01/11/2011

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: 01/11/2011

/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: 01/11/2011

/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 11/30/2010 (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. William F. Glavin, Jr.	/s/ Brian W. Wixted Brian W. Wixted
Date: 01/11/2011	Date: 01/11/2011