The teams played a doubleheader Friday after Thursday's scheduled opener was postponed by rain.
Jeremy Guthrie spun eight scoreless innings and Nick Markakis homered, as Baltimore edged Detroit, 2-1, in the nightcap. The Orioles also won the opener by a 10-6 score.
The wins made Orioles skipper Buck Showalter the first manager since 1900 to take over a team in August or later and win more games through the remainder of the season than the team had won before he took over the job.
Baltimore was 32-73 under Dave Trembley and Juan Samuel, and is 33-22 since Showalter assumed control on Aug. 3.
Guthrie (11-14) walked one, struck out five and did not allow a runner past second base, while Koji Ueharasurvived a bumpy ninth inning to earn his 12th save for the Orioles.
Robert Andino led a 13-hit attack by going 4-for-4 with a run scored, while Markakis and Adam Jones each had a pair of hits for the Birds, who have won four out of five.
Rick Porcello (10-12) was saddled with the loss after yielding both Baltimore runs on 12 hits while fanning four over 6 1/3 innings for the Tigers, who have dropped five straight.
Chris Tillman (2-5) was charged with one run on three hits and two walks while fanning seven to earn the game one victory. Detroit's Jeremy Bonderman (8-10) was tagged for nine runs on six hits, four walks and a pair of hit batters.
Matusz, a 23-year-old from Colorado, was 5-2 in eight starts with the Orioles last season and fell to 4-12 this year after a 7-3 loss at Tampa Bay on Aug. 14.
He's won five times and received two no-decisions since, however, as Baltimore has taken all seven starts.
The fourth overall pick in the 2008 draft has been particularly effective lately, allowing just one run on eight hits in his last three starts, covering 13 innings.
He's 1-0 lifetime against the Tigers and 3-7 in 15 home starts in 2010.
For Detroit, righty Armando Galarraga makes the final start of a season that'll be remembered for years for a June 2 outing.
The 28-year-old got within an eyelash of a perfect game in a 3-0 defeat of the Cleveland Indians, missing the gem after umpire Jim Joyce admitted blowing a call at first base with two outs in the ninth.
He's won just twice in 20 starts since as his earned run average has swelled from 2.57 to 4.62 and the Tigers have gone 8-12.
He was beaten, 6-3, by the Indians in his most recent start on Sept. 27 and has not beaten Baltimore in four career opportunities, going 0-2 with a 4.28 ERA in 27 1/3 innings.
Galarraga is winless since Aug. 20 and Detroit has lost his last seven starts.