Dan Straily tossed seven scoreless innings and Jed Lowrie added a key late solo homer as Oakland nipped Houston, 2-1, in the third portion of a four-game set.
Yoenis Cespedes also went deep for the Athletics, who have taken two of three in the series thus far and seven of nine overall.
Straily (9-7) allowed just two hits and one walk while striking out seven, and Sean Doolittle finished off the win by recording the final four outs to earn his first save.
"It's a different beast going out there for the save," Doolittle said. "That was a rush for sure."
Brandon Barnes drove in the lone run for the Astros, who skidded to their ninth defeat in the last 12.
Brett Oberholtzer (4-2) was the hard-luck loser, giving up seven hits and one run while fanning five in six full frames.
"He pitched very well," Astros manager Bo Porter said. "He left the one pitch up to Cespedes and Cespedes put a charge into but overall he did a tremendous job of battling and keep us right there."
The Athletics moved ahead 2-0 with Lowrie's two-out shot to center in the home seventh, but Houston halved its deficit in the eighth.
Dan Otero served up a one-out double to Brett Wallace, who went to third on a pinch single from Marc Krauss and scored on a Barnes fielder's choice grounder. Doolittle came on, and after stealing second, Barnes was caught trying to swipe third to end the inning.
Doolittle allowed a one-out single to Jose Altuve in the ninth, but retired Trevor Crowe and Jason Castro on fly outs to cap the narrow victory.
After seeing a potential run in Kurt Suzuki caught between third and home to end the third, Oakland hit the scoreboard in the fourth when Cespedes slugged a leadoff homer.
Straily set down the final nine he faced after a leadoff double by Matt Dominguez.
Straily's last scoreless outing came in a 1-0 win at Chicago on July 4, when he allowed one hit over seven innings ... Oakland has won 14 of 18 from Houston this season, including six of nine in California ... The top five batters in the A's order finished a combined 9-for-19.