Gatlin scored seven during a 24-0 run by Sam Houston State (19-5) to open the game and Texas College never threatened.
The Bearkats led 53-22 at halftime and Kyle McLeroy hit a pair of free throws with 4:15 left, giving Sam Houston State its biggest lead of the game, 82-32.
Percy Evans led Texas College with nine points.
The Steers shot 27 percent from the field, including 5 of 18 from 3-point range, and made just 8 of 16 free throws.
Sam Houston has won five games in a row and 14 of its last 15.