The win brought a smile to the face of interim manager Tony DeFrancesco, who has said he's been happy with how hard the club is playing despite winning only three times in his 14 games since taking over for Brad Mills on Aug. 19.
"Since I've been here, the fight's been there every game," he said. "I have no problem with the way guys are competing. A couple pitches executed here or there, a big hit here or there, it's a whole different story these last  games, but we're real pleased."
The top three hitters in the Astros' order -- Jose Altuve (2-for-5), Tyler Greene (2-for-4) and Wallace (3-for-4) -- went a combined 7-for-13 and scored all five runs. All three of Wallace's hits came against left-handed starter Jeff Locke, earning him a start Tuesday against former teammate, left-hander Wandy Rodriguez.
"It's something that I want to do, be in there every day and contribute," Wallace said. "The next step for me is to do it every day and to be able to do it against lefties, so I had a lot of opportunities with a guys getting on base in front of me -- Altuve and Greene. I tried to put swings on good pitches when they were there."
Gonzalez, making his first Major League start in nearly three years, held the Pirates to five hits and one run and struck out five batters for his first win since April 24, 2008, with the D-backs.
"This is the best thing that's happened to me this year -- to make the comeback to the big leagues, and I feel great," Gonzalez said. "I appreciate the Astros giving me the chance to throw in the big leagues, and I'm going to work hard every day to stay here."
Gonzalez had appeared in six games in the Mexican League in his hometown of Monterrey before signing with the Astros as a Minor League free agent on Aug. 23. He was paired Monday with catcher Chris Snyder, who caught him in Arizona.
"He's a good pitcher," said Pirates outfielder Garrett Jones, who had three of Pittsburgh's five hits. "He located well, kept the ball down, was able to change speeds on us. I was just trying to not do too much, take what he was giving me, because he wasn't really making too many mistakes. I just got a couple of balls on the bat to fall in. He was hitting spots well, and never seen him before. That's always tough. "
It only took the Astros four pitches to load the bases against Locke, as Altuve, Greene and Wallace all singled to start the game.
After Justin Maxwell hit into a fielder's choice that cut down Altuve at the plate, Matt Downs hit a comebacker off Locke's glove and was thrown out at first, driving in Greene. Maxwell plated Greene on a fielder's choice in the third to make it 2-0.
The top of the order sparked the Astros in the fifth, with Altuve and Greene reaching on one-out singles. Wallace then hit the first pitch of his at-bat from Locke over the wall in right-center field to give Houston a 5-0 lead. All seven of his homers this year have come on the road.
"I love hitting at Minute Maid, so I don't think it's anything like that," he said about the home/road discrepancy.
The Astros' bullpen, which coughed up a 3-0 lead Sunday against the Reds in Houston by allowing five runs in the eighth inning, backed Gonzalez by holding the Pirates hitless over the final 3 2/3 innings. Mickey Storey threw 1 2/3 innings and Wesley Wright tossed the final two innings.
Houston's max effort was on display in center field, where rookie Brandon Barnes nearly made a spectacular diving catch of a Jones fly ball in the second before crashing into the wall in the fifth trying to chase down a Pedro Alvarez fly ball.
"Pitching and defense was the answer," DeFrancesco said. "Barnes [0-for-4, four strikeouts] had a tough day at the plate, and in the field he had a great effort in the outfield. Unfortunately, one tipped off his glove and the other one he ran into the wall. Great effort, overall team effort today."