The Tigers (4-4, 3-1 Southwestern Athletic Conference) finished with 494 yards on offense, holding the Delta Devils (2-7, 1-5) to 173 yards.
Gilbert finished with 91 yards on 22 carries for the Tigers, who totaled 294 yards rushing.
Arvell Nelson ran for 85 yards on 12 carries, and was 25 of 43 for 289 yards and a touchdown for Texas Southern.
The Tigers took a 15-0 lead on a 21-yard field goal by Robert Hersh with 12:08 left in the second quarter.
Texas Southern had the ball within the Mississippi Valley State 20-yard line seven times, compared to just one red-zone appearance by the Delta Devils.
Mississippi Valley State was led by Eddie Ivory Jr. with 74 yards and a touchdown on 9-for-32 passing and 54 yards on 17 carries.