San Francisco, CA -- (Sports Network) - Roy Oswalt threw eight innings, retiring the final 14 batters he faced, as the Houston Astros continued their momentous May with a 7-3 win over the San Francisco Giants.

Lance Berkman continued his hot stretch, going 3-for-4 with a two-run homer for the Astros, who are 9-1 this month. Berkman tied a club record by scoring in his 15th straight game. He's on an 11-game hitting streak, batting .393 this season, including a .509 average since April 26.

"The guys are playing well and you want to try and win as many games as you can when its like this," Berkman said. "The offense hung around until we got the opportunity."

Oswalt (4-3), who won his fourth consecutive decision, allowed five hits and three runs while fanning six without issuing a walk. It was just his second win (2-5) in San Francisco.

Jose Valverde came on in the ninth inning and notched his ninth save. He retired pinch-hitter Ray Durham on a fly ball with the bases loaded to end the game, as Houston continued its success on a season-long 10-game road trip.

John Bowker hit a solo homer for the Giants, who have dropped six of their last eight games.

Barry Zito avoided moving to 0-8 this season as he had probably his best outing of the season, giving up seven hits and three runs over six innings in the no-decision. The lefty, pitching on the eve of his 30th birthday, walked one and struck out two. The three runs he received equaled the best run support he's had all season.

Vinnie Chulk (0-1) gave up the go-ahead run in the seventh inning and was saddled with the loss in the opener of the four-game series.

The Astros, coming off a sweep in Los Angeles, went ahead with a foul ball sacrifice fly in the seventh. Jose Cruz and Brad Ausmus singled to start the inning, and after Oswalt struck out, Hunter Pence lofted a fly ball tight to the line in right field. Randy Winn made the catch just in front of the stands, but his throw home was late as Houston took a 4-3 lead.

Houston loaded the bases in the next inning against Merkin Valdez on a Berkman double, an intentional walk to Carlos Lee and a beaning of Ty Wigginton. Cruz then singled to right field for a run, and Keiichi Yabu came in, but his pick- off try at first went wide and caromed down the right field line, allowing another run to score. To complicate matters, second baseman Eugenio Velez threw high to home plate, and the Astros went ahead 7-3.

Geoff Geary had trouble closing out the game in the ninth, and Rich Aurilia's bunt single off Valverde loaded the bases before Durham recorded the last out.

Fred Lewis and Omar Vizquel had back-to-back RBI doubles in the third for the Giants, and it became 3-0 in the fourth on Bowker's fourth homer of the season, a shot to right. However, Oswalt retired the next 14 hitters.

Houston tied it in the sixth. Pence and Mark Loretta singled to start the inning and Miguel Tejada followed with a sacrifice fly to right. Berkman then homered for the 13th time this season, a shot to left-center. The 13 homers ties Philadelphia's Chase Utley for the most in the majors this season.

Game Notes

Carlos Beltran also scored a run in 15 straight games for Houston during the 2004 season...Pence has a 10-game hitting streak...Ausmus recorded his 1,500th hit, becoming the eighth catcher to reach 1,500 hits and 100 steals...Vizquel played in his 2,573rd game at shortstop, which is 10 behind Luis Aparicio for most all-time.