WASHINGTON (AP) 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, which began a stretch in which it will play 14 of its next 17 games at home.
Zimmermann (10-3) allowed an unearned run on six hits, returning to form after surrendering six runs and eight hits in five innings Saturday in Cleveland.
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 35-year-old right-hander was signed to a minor league contract May 2, and went 3-2 with a 2.16 ERA in five starts for Double-A Tulsa before being called up.
Todd Helton and DJ LeMahieu had two hits for the Rockies, who have lost four straight and fell to .500 for the first time since April 2.
Zimmermann retired 16 straight in one stretch, throwing 112 pitches 85 for strikes while fanning nine and walking one.
Desmond, who hit a grand slam in the 11th inning of Wednesday's 6-2 win at Philadelphia, homered his first time up Thursday night to put Washington ahead 1-0 after two.
LaRoche led off the Washington fourth with a single. After Oswalt fanned Jayson Werth and Desmond, Lombardozzi singled. Kurt Suzuki then hit a grounder between third and short that shortstop Jonathan Herrera managed to deflect. Herrera retrieved the ball in short left, but LaRoche raced around from second and was safe on a close play at home to make it 2-0.
LaRoche provided some insurance in the fifth when he tripled with one out, scoring Span and Anthony Rendon.
Zimmermann drove in the Nationals' fifth run with a sacrifice fly the first of his career in the sixth.
Colorado finally got to Zimmermann in the eighth. Pinch hitter Josh Rutledge singled, Rendon committed a throwing error after fielding Tyler Colvin's grounder and Rutledge ended up on third. LeMahieu singled to score Rutledge, but Zimmermann struck out Carlos Gonzalez and Michael Cuddyer to end the threat.