Keuchel had his contract purchased from Triple-A Oklahoma City in order to make a spot start in place of right-hander Bud Norris.
Norris left his last start Tuesday with a sprained left knee.
Keuchel, a 2011 Texas League All-Star, was 5-4 with a 4.26 ERA over 80 1/3 innings in 13 starts with the RedHawks this season.
The University of Arkansas southpaw product was selected by the Astros in the seventh round of the 2012 First-Year Player Draft.
Keuchel, 24, will be the second Astros pitcher to make his big league debut in the 2012 campaign -- joining Rule 5 draftee Rhiner Cruz.
First pitch is scheduled for 2:05 p.m. CT.
The Rangers have already secured the Silver Boot Trophy for the 2012 regular season, thus marking six straight seasons in which Texas has captured the Lone Star Series against the Astros.