QuickLinks -- Click here to rapidly navigate through this document

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): April 4, 2005

FOREST OIL CORPORATION
(Exact name of registrant as specified in its charter)

New York
(State or other jurisdiction of incorporation)

1-13515   25-0484900
(Commission File Number)   (IRS Employer Identification No.)

1600 Broadway, Suite 2200, Denver, Colorado 80202
(Address of principal executive offices) (Zip Code)

303.812.1400
(Registrant's telephone number, including area code)

(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 (see General Instruction A.2.):

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 7.01. Regulation FD Disclosure.

        On April 4, 2005, Forest Oil Corporation ("Forest") announced that it completed the acquisition of a private company whose primary asset is an operated average working interest of 83% in the Buffalo Wallow Field and approximately 33,300 gross acres primarily in Hemphill and Wheeler Counties, Texas.

        Forest also provided an updated 2005 guidance.

        The information in this Current Report, including Exhibit 99.1, is being furnished pursuant to Item 7.01 of Form 8-K and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, or otherwise subject to liabilities of that section.


Item 9.01. Financial Statements and Exhibits.

2


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.


 
 
FOREST OIL CORPORATION
(Registrant)

Dated: April 4, 2005
 
By:
 
/s/  CYRUS D. MARTER IV      
Cyrus D. Marter IV
Vice President—General Counsel and Secretary

3


INDEX TO EXHIBITS FILED WITH THE CURRENT REPORT ON FORM 8-K

Exhibit
   Description
99.1   Forest Oil Corporation press release dated April 4, 2005, "Forest Oil Completes Acquisition of the Buffalo Wallow Field and Updates 2005 Guidance."



QuickLinks

SIGNATURES
INDEX TO EXHIBITS FILED WITH THE CURRENT REPORT ON FORM 8-K