George Springer also homered, Jose Altuve went 2-for-4 with two runs scored and Jon Singleton had two hits and an RBI in the win, only the Astros' second in 10 games. Cosart has been on the mound for each of those victories.
Cosart (8-5) did his part in this one as well, limiting the Braves to a run on six hits over seven innings to win his fourth consecutive outing.
Dominguez's blast was the big blow against Atlanta starter Mike Minor (2-5), who was reached for five runs in all over six innings of work.
Minor allowed seven hits, walked two and hit a batter, the latter of which proved costly with the game tied at 1-1 in the fourth inning. The lefty hit Dominguez to open the fourth, and Jason Castro followed with a double to deep center. Jesus Guzman was able to bring Dominguez home and send Houston ahead with a groundout one out later.
Dominguez made a greater impact in his next at-bat, crushing an 0-2 fastball from Minor with Altuve and Springer aboard in the fifth to extend the Astros' lead to 5-1. The homer halted an 0-for-23 skid at the plate for the third baseman.
Cosart took it from there, finishing out a string of six consecutive scoreless innings by stranding a pair of Braves in the top of the seventh. Houston then increased its margin in the bottom of the frame on Springer's laser off Juan Jaime that easily cleared the wall in left center.
Atlanta's lone run came quickly, as B.J. Upton led off the game with a single and was soon on third when Castro threw wildly on a stolen base attempt. Tommy La Stella followed with a sacrifice fly to center to give the Braves a 1-0 edge.
Houston answered in its half of the first when Altuve singled and raced home from first on Singleton's double off the left-field wall.