UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, DC  20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of
the Securities Exchange Act of 1934

Date of report (Date of earliest event reported) October 14, 2011

CORPORATE OFFICE PROPERTIES TRUST

(Exact name of registrant as specified in its charter)

6711 Columbia Gateway Drive, Suite 300
Columbia, Maryland 21046
(Address of principal executive offices)

(443) 285-5400
(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2 below):

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 2.02.              Results of Operations and Financial Condition

The information contained in Item 7.01 of this Current Report on Form 8-K regarding diluted earnings (loss) per share (“Diluted EPS”) and diluted funds from operations per share (“Diluted FFOPS”) of Corporate Office Properties Trust (the “Registrant”) for the three months ended September 30, 2011 is incorporated by reference into this Item 2.02.

Item 7.01.              Regulation FD Disclosure

On October 14, 2011, the Registrant issued a press release relating to its guidance for the three months ended September 30, 2011.  A copy of the press release is included as Exhibit 99.1 to this report and is incorporated by reference herein.

The information included in Items 2.02, 7.01 and 9.01 of this Current Report on Form 8-K, including the exhibit, shall not be deemed “filed” for any purpose, including the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or subject to liabilities of that Section.  The information included herein, including the exhibits, shall also not be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act regardless of any general incorporation language in such filing.

The Registrant uses non-GAAP financial measures in earnings press releases and information furnished to the Securities and Exchange Commission.  The Registrant believes that these measures are helpful to investors in measuring its performance and comparing such performance to other real estate investment trusts (“REITs”).  Descriptions of these measures are set forth below.

Funds from operations (“FFO” or “FFO per NAREIT”)

Defined as net (loss) income computed using GAAP, excluding gains on sales of previously depreciated operating properties and real estate-related depreciation and amortization.  Gains from sales of newly-developed properties less accumulated depreciation, if any, required under GAAP are included in FFO on the basis that development services are the primary revenue generating activity; we believe that inclusion of these development gains is in accordance with the National Association of Real Estate Investment Trust’s (“NAREIT”) definition of FFO, although others may interpret the definition differently and, accordingly, our presentation of FFO may differ from those of other REITs.  We believe that FFO is useful to management and investors as a supplemental measure of operating performance because, by excluding gains related to sales of previously depreciated operating properties and excluding real estate-related depreciation and amortization, FFO can help one compare our operating performance between periods.  We believe that net (loss) income is the most directly comparable GAAP measure to FFO.

Basic FFO available to common share and common unit holders (“Basic FFO”)

This measure is FFO adjusted to subtract (1) preferred share dividends, (2) income attributable to noncontrolling interests through ownership of preferred units in Corporate Office Properties, L.P. (the “Operating Partnership”) or interests in other consolidated entities not owned by us, (3) depreciation and amortization allocable to noncontrolling interests in other consolidated entities, (4) Basic FFO allocable to restricted shares and (5) issuance costs associated with redeemed preferred shares.  With these adjustments, Basic FFO represents FFO available to common shareholders and holders of common units in the Operating Partnership (“common units”).  Common units are substantially similar to our common shares of beneficial interest

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(“common shares”) and are exchangeable into common shares, subject to certain conditions.  We believe that Basic FFO is useful to investors due to the close correlation of common units to common shares.  We believe that net (loss) income is the most directly comparable GAAP measure to Basic FFO.

Diluted FFO available to common share and common unit holders (“Diluted FFO”)

Diluted FFO is Basic FFO adjusted to add back any changes in Basic FFO that would result from the assumed conversion of securities that are convertible or exchangeable into common shares.  The computation of Diluted FFO assumes the conversion of common units in the Operating Partnership but does not assume the conversion of other securities that are convertible into common shares if the conversion of those securities would increase Diluted FFO per share in a given period.  We believe that Diluted FFO is useful to investors because it is the numerator used to compute Diluted FFO per share, discussed below.  We believe that the numerator to diluted EPS is the most directly comparable GAAP measure to Diluted FFO.

Diluted FFO per share

Diluted FFO per share is (1) Diluted FFO divided by (2) the sum of the (a) weighted average common shares outstanding during a period, (b) weighted average common units outstanding during a period and (c) weighted average number of potential additional common shares that would have been outstanding during a period if other securities that are convertible or exchangeable into common shares were converted or exchanged.  The computation of Diluted FFO per share assumes the conversion of common units in the Operating Partnership but does not assume the conversion of other securities that are convertible into common shares if the conversion of those securities would increase Diluted FFO per share in a given period.  We believe that Diluted FFO per share is useful to investors because it provides investors with a further context for evaluating our FFO results in the same manner that investors use earnings per share (“EPS”) in evaluating net (loss) income available to common shareholders.  We believe that diluted EPS is the most directly comparable GAAP measure to Diluted FFO per share.

Item 9.01.                                          Financial Statements and Exhibits

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this Report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: October 14, 2011

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EXHIBIT INDEX

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