CHICAGO -- Roy Oswalt allowed four hits and came within two outs of a shutout and the Houston Astros ran their winning streak to six games with a 3-0 victory over the Chicago Cubs on Monday.

Associated Press

Roy Oswalt came within two outs of pitching a complete game shutout.

The Cubs have lost three straight, all at home -- their first three-game skid at Wrigley Field since August of last year. They remained 4 1/2 game ahead of the Brewers in the NL Central after Milwaukee lost 4-2 to the Mets.

Oswalt (13-9), who has won seven of his last eight decisions, took a two-hit shutout into the ninth. But pinch-hitter Daryle Ward and Alfonso Soriano hit back-to-back singles with one out before Jose Valverde was summoned from the bullpen.

Valverde got his 38th save in 44 chances when Kosuke Fukudome hit into a forceout and Derrek Lee flied out to the right field warning track to end the game.

Chicago hasn't had an extra base hit since Soriano homered in the seventh inning of Friday's game against the Phillies. The Cubs' last 27 hits have all been singles.

Miguel Tejada tripled to start the fourth against Jason Marquis (9-8) when he hit a line drive off the ivy-covered left-field wall and Soriano couldn't retrieve the ball. Lance Berkman walked and Geoff Blum hit a liner to center for a sacrifice fly with Berkman alertly taking second on the throw. Berkman then stole third and scored on Hunter Pence's RBI single for a 2-0 lead.

The Tejada/Berkman combination worked again in the seventh when Tejada singled and went to third on Berkman's single. Tejada scored on rookie Jeff Smardzija's wild pitch and Berkman made it all the way to third on an error by Cubs catcher Geovany Soto, who threw wildly past Samardzija as he covered the plate.

But the rally fizzled when Hunter Pence walked and was thrown out trying to steal.

Marquis went six innings and allowed five hits and two runs with a season-high eight strikeouts.

Notes:@ The Astros lead the season series 7-6. ... Houston has the fewest errors in the majors this season (58). ... Carlos Zambrano, scratched from his Sunday start to get extra rest for a tired arm, will pitch Tuesday night against Houston's Brandon Backe. ... Houston 2B Kaz Matsui, on the 15-day disabled list since August 13 with an irritated disk in his back, went through pregame drills. Manager Cecil Cooper is optimistic Matsui can return in the next few days. ... Battling the sun, Astros right fielder Pence made a great sliding catch of Mark DeRosa's sinking liner in the eighth.