Tapia was recalled from Triple-A Las Vegas on Sunday, Matt Kawahara of the San Francisco Chronicle reports.
Tapia was claimed off waivers by the A's in late April, and he'll now join the big-league club after spending the past month with Las Vegas. He has a 3.38 ERA, 1.20 WHIP and 10:6 K:BB over 13.1 innings at the Triple-A level this season.