Craig Biggio - 2 times
It isn't that surprising to see Craig Biggio on this list, but it is a little weird that he only managed to do so in 1997 and 1998. However, a closer look at his career numbers shows that the slugging side of things is what gave him trouble as those two seasons were the only seasons where he slugged .500 despite all those extra-base hits he racked up. He did get pretty close a few other times, though.
Cesar Cedeno - 2 times
We have to go back in time a bit for the next name on this list in Cesar Cedeno who managed to hit .300 and slug .500 in back-to-back seasons in 1972 and 1973. Cesar was an absolute stud during his time with the Astros as not only did he hit for average and a bit of power, but he was an absolute menace on the basepaths with 487 stolen bases in his 12 seasons with the Astros. His Hall of Fame case is also better than you may think.
Richard Hidalgo - 2 times
In the early 2000's, Richard Hildalgo's production was often overshadowed with guys like Biggio, Bagwell, and Berman around. However, he more than held his own during his time with the Astros and pulled this feat off twice in 2000 and 2003. He wasn't the most consistent guy at the plate, but he was better than many remember him being.
Yordan Alvarez is the start of the one-timers part of this list as he managed to hit .306 while slugging .613 just last season. Yordan is basically a mortal lock to slug .500 or better every season he plays, but he was also pretty close to hitting .300 this year as he sits at .293 in 488 plate appearances this season. If he didn't get hurt, it wouldn't have been shocking to see him do it in back to back seasons.