Ben Tate ran nine times for 95 yards and a score against the Saints' oft- porous run defense.
Foster capped the Texan's seven-play, 72-yard opening drive with a two-yard touchdown run.
Schaub played until the waning minutes of the first half, completing 12-of-16 passes for 163 yards. Johnson had four catches for 100 yards.
Brees finished 7-for-14 for 109 yards.
New Orleans backup Chase Daniel entered at the 8:31 mark of the second quarter and connected with Joe Morgan for a 56-yard touchdown strike. Morgan, a free agent rookie from Walsh, returned a punt 78-yards for a score in the Saints' preseason opener a week ago.
Mark Ingram, the Saints' No. 28 overall pick, ran seven times for 25 yards and a score.
Houston's Neil Rackers accounted for the lone second half scoring with a 40- yard field goal.
Brooks Reed, the Texans' second-round pick out of the University of Arizona, recorded two sacks.