Tatum, 28, played in 31 games for the Orioles in 2011 and hit .195 with three doubles and seven RBIs. He also appeared in 21 games for Triple-A Norfolk. Tatum has a .223 career average with one homer, 22 RBIs and 21 runs scored in 100 games with the Reds ('09) and Orioles ('10-11). He was selected by the Reds in the third round of the 2004 First-Year Player Draft.
The addition of Tatum to the Astros' 40-man roster leaves their total at 36, with Tatum joining fellow catchers Carlos Corporan, Humberto Quintero and Jason Castro (60-day disabled list).
Houston also re-signed outfielder Brandon Barnes to a Minor League contract with an invite to Major League Spring Training. In 630 career Minor League games, the 25-year-old owns a .250 average with 139 doubles, 21 triples, 77 homers and 300 RBIs. Barnes was selected by the Astros in the sixth round of the 2005 First-Year Player Draft.
Tim Bittner (Mid-Atlantic), Gavin Dickey (South Texas) and John Martin (Central and North Florida) also were announced as new amateur scout hires by Astros assistant general manager Bobby Heck.