Slowey and Blackburn had identical lines, allowing one hit with one walk and two strikeouts.
Slowey was 10-3 with a 4.86 ERA before undergoing season-ending reconstructive wrist surgery in July. The right-hander retired nine of his final 10 batters against Baltimore.
Blackburn also was sharp one day after he signed a $14 million, four-year contract.
Brian Matusz allowed two runs and three hits in 2 2-3 innings for Baltimore. He struck out six and walked one.
Koji Uehara worked a scoreless sixth for the Orioles.
Baltimore had just three hits.