Matt Schaub (14-of-26, 95 yards, one TD, two interceptions) found Foster with a pass along the goal line at the end of a seven-play, 66-yard drive with 4:21 to go in the first half, putting Houston up 10-3.
After Robbie Gould pulled the Bears within four points on a 24-yard field goal in the third quarter, Graham booted the second of his two scores with 4:55 left in the game to provide the final margin.
Foster carried the ball 29 times for 102 yards and made five catches for 15 more for the AFC South-leading Texans (8-1), who slogged to only 214 yards of total offense.
Jay Cutler went 7-of-14 passing for only 40 yards with two interceptions for the Bears (7-2) and didn't return for the second half after sustaining a concussion.
Brandon Marshall made eight grabs for 107 yards for Chicago.