Lowell and Coco Crisp hit solo homers; Kevin Youkilis hit a sacrifice fly; and Alex Gonzalez, who had four hits, belted an RBI single for the Red Sox (52-32), who won for the 16th time in their last 20 games.
In six innings, winner Jon Lester (4-0) scattered two runs and six hits. He had three walks and three strikeouts.
Boston has a three-game lead over the New York Yankees in the American League East.
Loser Mark Buehrle (9-6) gave up nine hits and five runs in 6 1/3 innings with no walks and three strikeouts.