Guthrie (11-14) gave up a leadoff single in the second and a two-out infield single in the fifth. He walked two and did not allow a runner past second base.
Koji Uehara came on in the ninth and retired the first two batters before giving up a homer to Don Kelly. Brandon Inge then singled, but Casper Wells struck out on three pitches to end the game and bring Uehara his 12th save.
The two wins Friday allowed Baltimore Manager Buck Showalter to reach a unique milestone. He became the first manager since 1900 to take over a team in August or September and win more games through the rest of the season that the team had won before he took the job.
The Orioles won 32 times under Dave Trembley and Juan Samuel and are 33-22 since Showalter arrived.
Baltimore had only two runs to show for 13 hits. Nick Markakis hit a solo homer in the third and Julio Lugo had an RBI single in the seventh.
Rick Purcell (10-12) was the hard-luck loser, giving up both runs on 12 hits in 6 1/3 innings.