Nick Markakis slugged a two-run homer as part of a five-run eighth inning to blow open the game. Markakis also singled twice, going 3-for-5 with two RBI and two runs.
Batting a solid .298, Markakis is one of the primary catalysts for the Orioles' August surge. He's riding a 10-game hitting streak and has hit safely in 15 of Baltimore 16 games this month, with eight multiple-hit games.
The Orioles now have a 7 1/2 game lead over the Yankees in the AL East and lead Toronto by eight games.
Game two of the series is Tuesday, at 8:10 pm EDT.
Atlanta, possibly positioning themselves for the wild card with four straight wins, took the initiative in the opening inning, scoring six runs off Pittsburgh starter Vance Worley.
Moving Jason Heyward into the leadoff spot may have been just the tonic the Braves needed. Heyward led off the game with his 10th home run, collected two more hits in four at-bats, and drove in Atlanta's final run with a sacrifice fly in the eighth.
The result left Atlanta six back of Washington in the East division, but 2 1/2 behind the Cardinals in the wild card chase, and, just one game behind the Giants for the second wild card.
Pittsburgh, meanwhile, slumped six games behind Milwaukee in the Central and now find themselves a game behind the Braves in the wild card, the series pivotal to both teams.
Game two is set for a 7:05 pm EDT start, Tuesday, in Pittsburgh.