The 6-foot Keenum spent last season on Houston's practice squad after signing as an undrafted free agent. The 6-3 McGee was a fourth-round pick by Dallas in 2009. He played in only three games for the Cowboys before he was cut at the end of training camp in 2012.
Defensive end Keith Browner, tight end Jake Byrne, receiver Jeff Maehl, linebackers Delano Johnson and Mike Mohamed and tackle Nick Mondek were also signed by Houston on Thursday. Maehl appeared in three games for Houston in 2011 after signing as an undrafted free agent. Mondek was a sixth-round pick by Houston in last year's draft.