Oregon Revised Statutes Elections § 254.535

(1) Except as provided in subsection (3) of this section, each tally sheet, return sheet and ballot return identification envelope shall be preserved for two years after the election to which it relates.

(2) Except as provided in subsection (3) of this section, the county clerk shall destroy the ballots and written challenge statements not sooner than the 90th day after the final day permitted for a contest of the election, unless otherwise ordered by the court.

(3) In accordance with 42 U.S.C. 1974, any ballot, voter registration records and any other materials relating to any election at which a candidate is nominated or elected to federal office shall be retained for not less than 22 months following the date of the election.