UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 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): November 27, 2012

Oglethorpe Power Corporation
(An Electric Membership Corporation)
(Exact name of Registrant as specified in its charter)

Registrant's telephone number, including area code (770) 270-7600

None
(Former name or former address, if changed since last report)

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:

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 2.03.    Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

        The information included in Item 8.01 of this Current Report on Form 8-K is incorporated by reference into this Item 2.03.

Item 8.01.    Other Events.

        On November 27, 2012, Oglethorpe Power Corporation (An Electric Membership Corporation) entered into an Underwriting Agreement with J.P. Morgan Securities LLC, as representative of the underwriters named therein, with respect to Oglethorpe's issuance and sale of an aggregate principal amount of $250,000,000 of 4.20% First Mortgage Bonds, Series 2012 A under Oglethorpe's Registration Statement on Form S-3 (File No. 333-167135) and related prospectus supplement and prospectus filed with the SEC. The first mortgage bonds are being issued pursuant to an Indenture dated March 1, 1997 between Oglethorpe, formerly known as Oglethorpe Power Corporation (An Electric Generation & Transmission Corporation), and U.S. Bank National Association, as trustee, successor to SunTrust Bank, Atlanta, as trustee, as supplemented by the Sixty-Third Supplemental Indenture dated as of November 1, 2012 between Oglethorpe and the trustee.

        The above-referenced underwriting agreement is filed as Exhibit 1.1 to this Current Report on Form 8-K. The above-referenced indenture and supplemental indenture (including the form of the first mortgage bonds) are filed as Exhibits 4.1 and 4.2, respectively, to this Current Report on Form 8-K. In connection with the issuance of the first mortgage bonds, Sutherland Asbill & Brennan LLP is providing the legal opinion attached to this Current Report on Form 8-K as Exhibit 5.1.

Exhibit 9.01 Financial Statements and Exhibits

(a)

Not applicable.

(b)

Not applicable.

(c)

Not applicable.

(d)

Exhibits

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SIGNATURE

        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.

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QuickLinks

Item 2.03. Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.
Item 8.01. Other Events.