O'Day, 29, was limited to 16 games for the Rangers in 2011 due to hip and shoulder injuries. He was 0-1 with a 5.40 ERA in 16 2/3 innings.
O'Day is 8-5 with a 2.89 ERA in 186 Major League appearances. He has 148 strikeouts against 49 walks in 180 2/3 innings.
O'Day began his MLB career with the Angels in 2008, making 30 appearances and going 0-1 with a 4.57 ERA before joining the Mets the following season as a Rule 5 Draft selection. The Rangers claimed him on waivers on April 22, 2009, and he became an important member of their bullpen. He went 2-1 with a 1.94 ERA in 64 games that season and was 6-3 with a 2.03 ERA in a team-high 72 appearances in 2010.
A Jacksonville, Fla., native, O'Day opened the 2011 season with Texas but was on the 60-day disabled list from April 27 to July 1 after undergoing surgery to repair a partial tear of the labrum in his left hip. He returned to the DL from Aug. 25 through Sept. 12 with right shoulder inflammation. He was a combined 1-0 with a 2.53 in 18 games with Double-A Frisco and Triple-A Round Rock and was not activated for any of the three postseason rounds for the American League champion Rangers.
The Orioles now have 38 players on their 40-man roster. Right-hander Jake Arrieta, infielder Brian Roberts and outfielder Luke Scott were reinstated from the 60-day disabled list on Wednesday.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.