Seth Smith also signed a one-year pact, leaving Brandon Moss and Jerry Blevins as the only Oakland players on the roster still eligible for arbitration.
Moss and Blevins will exchange figures with the A's on Friday, and arbitration hearings are scheduled from Feb. 4-20, if necessary. Teams and players can negotiate on a contract all the way up to their hearing date, however, and most often arbitration is avoided before a court hearing.
Jaso, 29, was brought over from Seattle in a three-team trade on Wednesday, when the Mariners reeled in outfielder/first baseman Michael Morse from the Nationals, who in turn received three Minor Leaguers from the A's, including highly touted prospect A.J. Cole.
Jaso hit .276 with a .394 on-base percentage, 10 home runs and 50 RBIs in 108 games for the Mariners last year. He figures to be a staple in Oakland's lineup against right-handers, much like the left-handed Smith.
Smith hit .240 with 14 home runs and 52 RBIs in 125 games while sharing time in both left field and at designated hitter last year for the A's, who plan to use him mostly at DH this season.
Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.