Exhibit 99.1

Earnings Release & Supplemental Information — Unaudited

March 31, 2012

Please refer to the section entitled “Definitions” for definitions of non-GAAP measures and other terms we use herein that may not be customary or commonly known.

COPT REPORTS FIRST QUARTER 2012 RESULTS

COLUMBIA, MD April 26, 2012 — Corporate Office Properties Trust (COPT) (NYSE: OFC), an office real estate investment trust (REIT) that focuses primarily on serving the specialized requirements of U.S. Government and Defense Information Technology tenants, announced financial and operating results for the first quarter ended March 31, 2012.

“While we continue to operate in a challenging economic environment, 2012 is starting off well, as evidenced by our quarterly results,” stated Roger A. Waesche, Jr., President and Chief Executive Officer of Corporate Office Properties Trust. “We continue to make solid progress executing on our Strategic Reallocation Plan and we are pleased with the performance of our same office portfolio,” he added.

Results:

Diluted earnings per share (EPS) was $0.04 for the quarter ended March 31, 2012 as compared to an EPS loss of ($0.33) in the first quarter of 2011. Diluted funds from operations per share (FFOPS), as adjusted for comparability, was $0.53 for the first quarter ended March 31, 2012, which represented an 8% increase from the $0.49 reported for the first quarter of 2011. Adjustments for comparability encompass items such as acquisition costs, impairments and gains on non-operating properties, gains (losses) on early extinguishment of debt and derivative losses. Please refer to the reconciliation tables that appear later in this press release. Per NAREIT’s definition, FFOPS for the first quarter of 2012 was $0.54 versus $0.13 reported in the first quarter of 2011.

Operating Performance:

Portfolio Summary — At March 31, 2012, the Company’s consolidated portfolio of 231 operating office properties totaled 20.2 million square feet. The weighted average remaining lease term for the portfolio was 4.7 years and the average rental rate (including tenant reimbursements) was $26.95 per square foot. The Company’s consolidated portfolio was 87% occupied and 89% leased as of March 31, 2012, up 80 and 70 basis points, respectively, from December 31, 2011 levels.

Same Office Performance — The Company’s same office portfolio excludes properties identified for eventual disposal as part of the Company’s Strategic Reallocation Plan. For the quarter ended March 31, 2012, COPT’s same office portfolio represents 79% of the rentable square feet of the portfolio and consists of 169 properties. The Company’s same office portfolio occupancy was 89.5% at the end of the first quarter of 2012, down 10 basis points from year end 2011.

For the first quarter ended March 31, 2012, the Company’s same office property cash NOI, excluding gross lease termination fees, increased 7% as compared to the first quarter ended 2011. Including gross lease termination fees, same office property cash NOI for the first quarter ended March 31, 2012 increased 8% over the same period in 2011.

Leasing — COPT leased a total of 570,000 square feet during the quarter ended March 31, 2012, which included 86,000 square feet of development leasing. During this same period, the Company’s renewal rate was 59%. For the quarter ended March 31, 2012, total rent on renewed space increased 2% as measured from the straight-line rent in effect preceding the renewal date; on a cash basis, renewal rents decreased 8%.

Investment Activity:

Construction — At March 31, 2012, the Company had six office properties totaling 789,000 square feet under construction for a total projected cost of $197.7 million, of which $136.4 million had been incurred.

Dispositions — In the first quarter of 2012, COPT sold seven stabilized properties, two vacant properties and a land parcel for net proceeds of approximately $61 million. The stabilized buildings contained an aggregate of 219,000 square feet and were 80% occupied (63 leases) at the time of sale.

Capital Transactions:

In February, the Company entered into a $250 million term loan agreement with its bank group. The Term Loan has a five-year term and a variable interest rate of LIBOR plus 1.65% to 2.40%, depending on the Company’s leverage levels. The Company used proceeds from the Term Loan to repay outstanding balances on its unsecured line of credit.

Balance Sheet and Financial Flexibility:

As of March 31, 2012, the Company had a total market capitalization of $4.4 billion, with $2.4 billion in debt outstanding, equating to a 55% debt-to-total market capitalization ratio. Also, the Company’s weighted average interest rate was 4.37% for the quarter ended March 31, 2012 and 80% of the Company’s debt was subject to fixed interest rates, including the effect of interest rate swaps.

For the first quarter 2012, the Company’s adjusted EBITDA to interest expense coverage ratio was 3.20x, and the adjusted EBITDA fixed charge coverage ratio was 2.72x. Adjusting for construction in progress, the Company’s adjusted debt-to-adjusted EBITDA ratio was 6.69x for the three months ended March 31, 2012.

2012 FFO Guidance:

Management is affirming its previously issued guidance for 2012 FFOPS of between $2.02 and $2.18, and is issuing second quarter 2012 FFOPS guidance of $0.48 to $0.52. A reconciliation of projected diluted EPS to projected FFOPS for the quarter ending June 30, 2012 and the year ending December 31, 2012 is provided, as follows:

Conference Call Information:

Management will discuss first quarter 2012 earnings results, as well as its 2012 guidance, on its conference call today at 11:00 a.m. Eastern Time, details of which are listed below:

Please use the following link to pre-register and view important information about this conference call. Pre-registering is not mandatory but is recommended as it will provide you immediate entry into the call and will facilitate the timely start of the conference. Pre-registration only takes a few moments and you may pre-register at anytime, including up to and after the call start time. To pre-register, please click on the below link:

https://www.theconferencingservice.com/prereg/key.process?key=PJAUAWVD7

You may also pre-register in the Investor Relations section of the Company’s website at www.copt.com. Alternatively, you may be placed into the call by an operator by calling the number provided above at least 5 to 10 minutes before the start of the call. A replay of this call will be available beginning Thursday, April 26 at 3:00 p.m. Eastern Time through Thursday, May 10 at midnight Eastern Time. To access the replay within the United States, please call 888-286-8010 and use passcode 94646315. To access the replay outside the United States, please call 617-801-6888 and use passcode 94646315.

The conference calls will also be available via live webcast in the Investor Relations section of the Company’s website at www.copt.com. A replay of the conference calls will be immediately available via webcast in the Investor Relations section of the Company’s website.

Company Information:

COPT is an office REIT that focuses primarily on strategic customer relationships and specialized tenant requirements in the U.S. Government and Defense Information Technology sectors and Data Centers serving such sectors. The Company acquires, develops, manages and leases office and data center properties that are typically concentrated in large office parks primarily located adjacent to government demand drivers and/or in strong markets that we believe possess growth opportunities. As of March 31, 2012, the Company’s consolidated portfolio consisted of 231 office properties totaling 20.2 million rentable square feet. The Company’s portfolio primarily consists of technically sophisticated buildings in visually appealing settings that are environmentally sensitive, sustainable and meet unique customer requirements. COPT is an S&P MidCap 400 company and more information can be found at www.copt.com.

Forward-Looking Information:

This press release may contain “forward-looking” statements, as defined in Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, that are based on the Company’s current expectations, estimates and projections about future events and financial trends affecting the Company.  Forward-looking statements can be identified by the use of words such as “may,” “will,” “should,” “could,” “believe,” “anticipate,” “expect,” “estimate,” “plan” or other comparable terminology.  Forward-looking statements are inherently subject to risks and uncertainties, many of which the Company cannot predict with accuracy and some of which the Company might not even anticipate.  Accordingly, the Company can give no assurance that these expectations, estimates and projections will be achieved.  Future events and actual results may differ materially from those discussed in the forward-looking statements.

Important factors that may affect these expectations, estimates, and projections include, but are not limited to:

·                  general economic and business conditions, which will, among other things, affect office property and data center demand and rents, tenant creditworthiness, interest rates, financing availability and property values;

·                  adverse changes in the real estate markets including, among other things, increased competition with other companies;

·                  governmental actions and initiatives, including risks associated with the impact of a government shutdown or budgetary reductions or impasses, such as a reduction in rental revenues,  non-renewal of leases, and/or a curtailment of demand for additional space by strategic tenants;

·                  the Company’s ability to sell properties included in its Strategic Reallocation Plan;

·                  the Company’s ability to borrow on favorable terms;

·                  risks of real estate acquisition and development activities, including, among other things, risks that development projects may not be completed on schedule, that tenants may not take occupancy or pay rent or that development or operating costs may be greater than anticipated;

·                  risks of investing through joint venture structures, including risks that the Company’s joint venture partners may not fulfill their financial obligations as investors or may take actions that are inconsistent with the Company’s objectives;

·                  changes in the Company’s plans or views of market economic conditions or failure to obtain development rights, either of which could result in recognition of impairment losses;

·                  the Company’s ability to satisfy and operate effectively under Federal income tax rules relating to real estate investment trusts and partnerships;

·                  the dilutive effect of issuing additional common shares; and

·                  environmental requirements.

The Company undertakes no obligation to update or supplement any forward-looking statements. For further information, please refer to the Company’s filings with the Securities and Exchange Commission, particularly the section entitled “Risk Factors” in Item 1A of the Company’s Annual Report on Form 10-K for the year ended December 31, 2011.

Reconciliations:

Reconciliations of non-GAAP measures to the most directly comparable GAAP measures are included in the tables, below. Please refer to the information furnished with our Form 8-K on our website (www.copt.com) for definitions of these non-GAAP measures and other terms used in this press release.

Corporate Office Properties Trust

Summary Financial Data

(unaudited)

(Amounts in thousands, except per share data)

Corporate Office Properties Trust

Summary Financial Data

(unaudited)

(Amounts in thousands, except per share data and ratios)

(1)          Represents debt as of period end divided by Adjusted EBITDA for the period, as annualized (i.e. three month periods are multiplied by four).

(2)          Represents debt adjusted to subtract construction in progress as of period end divided by Adjusted EBITDA for the period, as annualized (i.e. three month periods are multiplied by four).

Corporate Office Properties Trust

Summary Financial Data

(unaudited)

(Dollars and shares in thousands, except per share data)

Corporate Office Properties Trust

Summary Financial Data

(unaudited)

(Dollars in thousands)

Summary Description

The Company — Corporate Office Properties Trust (the “Company” or “COPT”) is a self-managed office real estate investment trust (“REIT”). As of March 31, 2012, COPT derived 60% of its annualized rental revenue from properties occupied primarily by tenants in the U.S. Government and/or defense information technology (“Defense IT”) sectors and 83% of the Company’s square footage was located in the Greater Washington/Baltimore region. At March 31, 2012, COPT’s operating portfolio of 231 office properties encompassed 20.2 million square feet and was 88.9% leased. As of the same date, COPT also owned one wholesale data center that was 17% leased.

Corporate Strategy — Through acquisitions and development activities, COPT has assembled a portfolio of Class-A office parks located adjacent to knowledge-based defense installations (rather than weapons production-oriented bases) that are executing programs deemed critical to the nation’s current and future security. COPT also owns dedicated data centers that serve the specialized requirements of our government and Defense IT tenants and a wholesale data center.

Disclosure Statement — This supplemental package contains forward-looking statements within the meaning of the Federal securities laws. Forward-looking statements can be identified by the use of words such as “may,” “will,” “should,” “could,” “believe,” “anticipate,” “expect,” “estimate,” “plan” or other comparable terminology.  Forward-looking statements are inherently subject to risks and uncertainties, many of which we cannot predict with accuracy and some of which we might not even anticipate.  Although we believe that the expectations, estimates and projections reflected in such forward-looking statements are based on reasonable assumptions at the time made, we can give no assurance that these expectations, estimates and projections will be achieved.  Future events and actual results may differ materially from those discussed in the forward-looking statements.  Important factors that may affect these expectations, estimates and projections include, but are not limited to: general economic and business conditions, which will, among other things, affect office property and data center demand and rents, tenant creditworthiness, interest rates, financing availability and property values; adverse changes in the real estate markets, including, among other things, increased competition with other companies; governmental actions and initiatives, including risks associated with the impact of a government shutdown or budgetary reductions or impasses, such as a reduction in rental revenues, non-renewal of leases and/or a curtailment of demand for additional space by our strategic customers; our ability to sell properties included in our Strategic Reallocation Plan; our ability to borrow on favorable terms; risks of real estate acquisition and development activities, including, among other things, risks that development projects may not be completed on schedule, that tenants may not take occupancy or pay rent or that development and operating costs may be greater than anticipated; risks of investing through joint venture structures, including risks that our joint venture partners may not fulfill their financial obligations as investors or may take actions that are inconsistent with our objectives; changes in our plans for properties or views of market economic conditions or failure to obtain development rights, either of which could result in recognition of impairment losses; our ability to satisfy and operate effectively under Federal income tax rules relating to real estate investment trusts and partnerships; the dilutive effects of issuing additional common shares; and environmental requirements.  We undertake no obligation to update or supplement any forward-looking statements.  For further information, please refer to our filings with the Securities and Exchange Commission, particularly the section entitled “Risk Factors” in Item 1A of our Annual Report on Form 10-K for the year ended December 31, 2011.

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Corporate Office Properties Trust

Equity Research Coverage

With the exception of Green Street Advisors, the above-listed firms are those whose analysts publish research material on the Company and whose estimates of our FFO per share can be tracked through Thomson’s First Call Corporation. Any opinions, estimates, or forecasts the above analysts make regarding COPT’s future performance are their own and do not represent the views, estimates, or forecasts of COPT’s management.

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Corporate Office Properties Trust

Selected Financial Summary Data

(in thousands, except per share data)

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Corporate Office Properties Trust

Selected Portfolio Data