Jordan Zimmermann pitched eight innings to win his 10th game, Adam LaRoche had three hits including a two-run triple and the Nationals spoiled Roy Oswalt's return to the majors with a 5-1 win over the Colorado Rockies on Thursday night.
Ian Desmond homered for the second straight game, and Denard Span and Steve Lombardozzi added a double and a single apiece for Washington.
Zimmermann (10-3) allowed an unearned run on six hits. He retired 16 straight in one stretch, throwing 112 pitches -- 85 for strikes -- while fanning nine and walking one.
Oswalt (0-1) went five innings in his Colorado debut, allowing four runs on nine hits. He struck out 11 and didn't walk a batter.
The Rockies have lost four straight and fell to .500 for the first time since April 2.