Howard was recalled from Triple-A Round Rock ahead of his start against the Orioles on Tuesday.
The 25-year-old opened the season in the majors but has been at Triple-A since late April, and he has a 3.69 ERA, 1.26 WHIP and 60:19 K:BB over 46.1 frames in 10 starts for Round Rock. Howard is now taking the big-league rotation spot of Taylor Hearn, who was demoted to the minors last week.