The Astros recalled Bielak from Triple-A Sugar Land on Tuesday, Brian McTaggart of MLB.com reports.
Bielak has pitched to a 3.58 ERA in 27.2 innings since being sent down July 21. Prior to the demotion, the righty had a 3.48 mark in 10.1 big-league innings and he figures to handle long-relief work for however long he's with the Astros.