San Francisco, CA -- (Sports Network) - Roy Oswalt hurled eight innings of one- run ball, and the Astros salvaged the last of this three-game set with a 7-1 victory over the Giants.

Oswalt (5-4), coming off his best effort of the season -- a complete game two- hitter against San Diego -- gave up just three hits with six strikeouts compared to just one walk. Over his last three outings, spanning 23 innings, the veteran right-hander has allowed just 12 hits and three runs.

"To start the road trip and end the road trip with two great performances (by Oswalt). Last time out, I thought he had good stuff and this time I think his stuff was even better. I hope this is something we'll see a lot of this second half and if it is, we'll jump on his back and ride it," Astros manager Cecil Cooper said.

Houston entered the series winners in six of its previous eight but managed just seven hits over the first two games. Houston eclipsed that feeble mark with 10 hits on Sunday, three of which came from Jeff Keppinger, who also scored twice and knocked in one.

Oswalt helped himself with a two-run single while Miguel Tejada, Hunter Pence and Jason Michaels each homered in the rout. Tejada and Pence did so after being named to the N.L. All-Star team as reserves earlier in the day.

The tables were turned Sunday against the Giants, who had outscored the 'Stros 22-0 en route to winning the first two games. San Francisco had just three hits, one of those a Rich Aurilia solo home run.

Randy Johnson (8-6), attempting to win a third consecutive start and fourth straight decision, allowed five hits and four runs, three of those earned. The lanky lefty was forced to leave the game in the fourth with an injured left shoulder. The initial diagnosis is a strain.

The injury appeared to come in the third on an awkward wave at a third-strike curveball from Oswalt. He immediately reached for the shoulder but remained for the fourth, where he yielded three of his runs and committed a throwing error before leaving.

"Very scary. I thought he did something to (his left shoulder) and started throwing a lot slower than he usually throws...89-91 and all of the sudden you see this guy throwing 82. You just hope and pray that nothing happens to him seriously and that he's okay for the next start," said battery mate Bengie Molina of Johnson.

Tejada started the scoring with a solo home run in the first, and Houston padded its lead in the fourth, when Pence and Michaels took the ailing Johnson deep for solo shots. Keppinger followed with a two-out single, and Oswalt sent a dribbler back to the mound that Johnson threw past first and down the right field line, allowing Keppinger to cross the plate for a 4-0 margin.

Johnson quickly exited, and Justin Miller and Bob Howry helped limit the damage over the next three frames. Merkin Valdez, however, was hurt for three runs in the eighth, as Houston gained a 7-0 advantage. With runners at the corners and two out, Keppinger doubled to right, scoring Michael Bourn, and Oswalt came through with a two-run base hit to left.

Aurilia landed the lone blemish on Oswalt's line with a solo shot in the eighth. Oswalt finished out the frame, and LaTroy Hawkins polished off the win with a perfect ninth.

Game Notes:

Bourn swiped his 27th base of the season...Oswalt threw 94 pitches, 69 for strikes. He has 22 strikeouts and just five walks over his last three starts...The Giants will have Tim Lincecum and Matt Cain representing the team at this year's All-Star game...The 'Stros finished off their seven-game road trip 4-3. They next return home for seven straight starting Monday against Pittsburgh...San Francisco will host Florida and San Diego on a seven-game homestand.