Making his first major league start in more than eight months, Oswalt pitched effectively into the seventh inning and the Rangers won their seventh straight game, beating the slumping Colorado Rockies 4-1 on Friday night.
Oswalt, who pitched more than 10 years in the National League with Houston and Philadelphia, made four minor league starts after signing with the Rangers on May 29.
The 34-year-old Oswalt won his 160th career game and his first since beating Atlanta on Sept. 27. He allowed nine hits and one run in 6 2/3 innings.
"I won't tell you I wasn't nervous," said Oswalt, who threw 81 of his 110 pitches for strikes. "If you don't have butterflies, you might as well get out of the game."
Oswalt last pitched in the majors Oct. 5 -- a Game 4 loss to the St. Louis Cardinals in the NL Division Series.
The Rockies probably felt the time off hadn't hurt Oswalt. The right-hander improved to 9-2 lifetime against Colorado with a 1.89 ERA, his best mark against any of the 16 teams he's faced more than three times.
"He was ready to pitch and he pitched like Roy Oswalt," Rangers manager Ron Washington said.
Christian Friedrich (4-4) allowed four runs and seven hits in six innings for the Rockies, who have lost 13 of 15.
Oswalt, who struck out six and walked one, was sharp from the start. His fastball was clocked in the low 90s and he showed off his slow curveball that confused Colorado hitters most of the game.
The Rockies didn't muster much against Oswalt until breaking through in the seventh.
Joe Nathan pitched a perfect ninth to earn his 16th save in 17 chances. This is the Rangers' longest winning streak since taking eight straight April 12-21.
"These guys have been rolling," Oswalt said. "I was just trying to keep it going."
Wilin Rosario had three hits for the Rockies, who dropped to 1-12 in interleague play.
The Rockies left 10 men on base in the game and hit into double plays in the seventh and eighth.
"We didn't play a bad ballgame at all," Colorado manager Jim Tracy said. "We had a bunch of hits. We just couldn't get the big hits."
Beltre hit a two-run homer in the first that just cleared the fence in right. It was his 13th of the season.
Nelson Cruz had an RBI double before Napoli lined his 12th home run of the season to right to make it 4-0 in the fourth.
To make room for Oswalt on the roster, 1B Mitch Moreland (left hamstring strain) was placed on the 15-day DL. ... Rockies IF Jonathan Herrera was activated from the 15-day DL Friday and made his third career start at SS. ... Rangers LHP Derek Holland (left shoulder fatigue) threw 42 pitches in a bullpen session. He will throw again in the bullpen Sunday or Monday. ... Beltre hit a liner off Friedrich's back in the fourth, but the left-hander remained in the game.