The Red Sox wrapped up no worse than a wild card berth and moved to the edge of clinching the American League East title. Boston became the first American League team to earn a post-season spot.
Lackey (10-12) walked two men through six innings and did not give up a hit until Adam Jones homered with one out in the seventh. Baltimore's other hit came on a single by J.J. Hardy in the eighth.
It was the 16th complete game of Lackey's 12-year career. He walked two, struck out eight and threw 113 pitches.
Chris Tillman (16-7) gave up the three runs along with seven hits in seven innings to take the loss. He struck out eight.
Baltimore had a three-game winning streak snapped and was officially eliminated from the division title chase. The Orioles began the night two games out of the top wild card spot and one game behind in the chase for the second wild card position.