PHILADELPHIA -- Roy Oswalt was back to his old self, mixing in nasty off-speed pitches with a sharp fastball.
"He was vintage Roy," Astros manager Cecil Cooper said. "He kept the ball down, had a nice breaking ball and his fastball was crisp. He pitched real well."
Bourn connected off Kyle Kendrick (1-2) in the fifth inning to help beat his former teammates a night after the Phillies scored four runs off closer Jose Valverde to win in the bottom of the ninth.
Oswalt (1-3) finally looked like a three-time All-Star instead of the worst pitcher in the NL. The right-hander gave up one run and five hits to snap a three-game skid and beat the Phillies for the sixth straight time. Oswalt came in first or tied for first in the league in losses, runs and hits allowed.
"Hopefully I turned it around," Oswalt said. "I felt better. I wasn't overthrowing. I feel when I have my curveball, I should be able to get to the eighth or ninth inning."
Wesley Wright struck out the side in the eighth and Doug Brocail finished for his first save since earning one with Texas in 2005. Valverde couldn't protect a 3-0 lead Tuesday night. He allowed two homers and a game-winning RBI double while recording just one out.
Valverde had a bullpen session before the game, so Cooper held him out until the next save situation.
"He's our closer no question about it," Cooper said.
The Phillies sorely missed 2007 NL MVP Jimmy Rollins, who was out of the starting lineup for the seventh straight game because of a sprained left ankle. Rollins won't return until Saturday at the earliest because he's heading to Oakland, Calif., to attend a funeral for an uncle.
Rollins ripped a two-out single as a pinch hitter in the ninth inning. He hobbled to first base and was replaced by pinch-runner So Taguchi. Brocail then struck out pinch-hitter Greg Dobbs to end it.
Bourn, a speedy leadoff hitter, turned on an inside pitch and hit it high off the right-field foul pole to give the Astros a 2-1 lead in the fifth.
Bourn was a valuable part of Philadelphia's division-winning team last year, contributing as a late-inning defensive replacement, pinch runner and filling in as a starter when other outfielders were injured. With center fielder Shane Victorino on the disabled list, the Phillies sure could use Bourn right now.
Bourn was traded to the Astros along with reliever Geoff Geary and minor leaguer Mike Costanzo for closer Brad Lidge last November.
"You always want to play well against the team the traded you," Bourn said. "More importantly, we got the win. I'm glad we bounced back the way we did. I can't be mad at them. They gave me my opportunity last year. I'm happy where I'm at now."
Kendrick went seven innings, allowing two runs and four hits in his best outing so far. The right-hander struck out five and walked one.
Kendrick lasted a total of 7 1/3 innings in his first two starts, but resembled the pitcher who came from nowhere - actually, Double-A - and won 10 games last season to help the Phillies win the NL East.
"He was more aggressive," manager Charlie Manuel said. "His command was good, good location with his sinker. He showed last year that he's durable. I have confidence in him."
Carlos Lee's RBI double off the left-field wall gave the Astros a 1-0 lead in the first. Ryan Howard tied it with a two-out RBI single in the bottom half.
Oswalt hasn't lost to the Phillies since May 9, 2003. He's 6-1 lifetime against Philadelphia. His six-game winning streak against the Phillies is the longest by any pitcher since Tom Glavine won seven in a row with Atlanta from 1990-92.
Two other Astros pitchers have won six straight decisions against the Phillies. Dave Roberts did it from 1972-73 and Turk Farrell from 1963-64. ... Bourn is 8-for-8 on steal attempts after swiping second base in the first inning.