Ramon Hernandez and Aubrey Huff each drove in two runs and Kevin Millar homered for the Orioles. Brandon Fahey added two hits.
Ian Kennedy (0-2) had another rough outing for the Yankees, giving up four runs and five hits with five walks to raise his ERA to 9.64. New York lost its third straight.
It was the third straight win for the Orioles, who remained half a game behind Boston in the AL East.
Joba Chamberlain pitched a scoreless eighth inning for New York. Chamberlain returned to the team earlier in the day after missing five games to attend to his sick father in Nebraska.
In the first inning, Derek Jeter hit a two-out triple just past the glove of a diving Nick Markakis. Alex Rodriguez then reached on a squibber in front of the plate, with Jeter holding at third. Burres got out of the inning when Posada grounded to shortstop for a force out.
The Yankees also had runners at first and second with one out in the second, but Jose Molina hit into a double play.
Baltimore took a 1-0 lead in the second on back-to-back doubles by Hernandez and Fahey.
Millar put the Orioles up 2-0 with his third home run of the season, a 390-foot solo shot to left. Luke Scott and Huff walked and Hernandez's two-out double scored both runners to make it 4-0.
The Orioles added two more runs in the seventh on a one-out double by Huff which scored Markakis and Millar. Brian Roberts almost added to he lead, but his bases-loaded liner was stopped on a diving stab by Jorge Posada, who started at first base. It was just his 19th appearance there in 1,445 games.
