Oregon Revised Statutes Public Officers and Employees § 238.157

(1) Any person who entered or reentered active service in the Armed Forces of the United States after January 1, 1950, for other than active duty for training, or who was in active service in the Armed Forces of the United States on January 1, 1950, for other than active duty for training, and who, after being other than dishonorably discharged therefrom, entered the employ of an employer participating in the Public Employees Retirement System, may acquire retirement credit for up to four years of active service in the Armed Forces by paying in a lump sum to the Public Employees Retirement Board within 90 days of the member's effective date of retirement an amount determined by the board to represent the full cost to the system of providing the retirement credit to the member, including all administrative costs incurred by the system in processing the application for acquisition of the retirement credit.

(2) No person shall receive retirement credit under this section for any period of service with the Armed Forces of the United States for which that person receives credit under the provisions of ORS 238.156 or for which the person is receiving or entitled to receive a pension or retirement pay under a public retirement system established by the United States for the performance of service in the Armed Forces.

(3) Any person acquiring retirement credit under this section may elect to have the service retirement allowance of the person determined under any calculation for which the person is eligible under ORS 238.300, even if the calculation does not produce the largest service retirement allowance. An election under this subsection must be made within 90 days of the member's effective date of retirement.