Crosby had been on the DL since Aug. 18 with a strained left calf. A free agent at the end of the season, he'll see time at first base against left-handed starting pitchers in the final month and occasionally spell regular third baseman Adam Kennedy.
The 2004 American League Rookie of the Year, Crosby, 29, lost his starting shortstop job this year and is all but certain he'll be moving on. Orlando Cabrera was the starting shortstop until he was traded before the July 31 deadline, after which Cliff Pennington was handed the job.
Meloan has played in four different organizations this year, having started the season in Triple-A ball with the Indians. He was traded to the Rays organization July 2 and picked up off waivers by the Pirates on Aug. 12.
All told, Meloan has posted a 4.57 ERA in 41 games with three Triple-A teams this year. After claiming Meloan, the A's optioned him to Triple-A Sacramento.
Mychael Urban is a national reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.