Oswalt pitched six innings, allowing two runs on six hits and a walk with five strikeouts on Sunday night for Triple-A Round Rock. He threw 100 pitches, 70 for strikes, and was the winning pitcher in the Express' 4-2 victory against the Oklahoma City RedHawks in Round Rock, Texas.
Oswalt had two 1-2-3 innings, and five of the hits he allowed were singles. The only extra-base hit was a sixth-inning double by Mike Hessman.
The injury-depleted Rangers have not indicated when they expect Oswalt to return to the majors. Two regular members of their rotation -- Neftali Feliz and Derek Holland -- and replacement starter Alexi Ogando are on the disabled list.
Scott Feldman has been ineffective, failing to win a game in five starts since taking over Feliz's spot in the rotation. Rookie Justin Grimm gave the Rangers a shot in the arm Saturday, throwing six innings and getting the win in his major league debut after being called up from Double-A Frisco.
Through Oswalt's first three minor league starts, two for Round Rock and one for Frisco, he had a 7.71 ERA over 9 1/3 innings with eight strikeouts and three walks.
In his last start before Sunday's, Oswalt needed 85 pitches to get through 3 1/3 innings for Frisco, giving up three earned runs on five hits.
Oswalt, 34, pitched for the Philadelphia Phillies in the latter part of 2010 and all of 2011. Prior to that, he spent more than nine seasons with the Houston Astros. He has a career record of 159-93 with a 3.21 ERA.
When the Rangers signed him to a free-agent deal last month, Oswalt said he'd been throwing regular bullpen sessions and thought he could be ready to join the Rangers' rotation after four minor league starts.