It was the third win of the tournament for Utah State (9-1), which has won nine of its first 10 games since 2008-09, when the Aggies went 24-1.
Utah State was 24 of 60 from the floor (60 percent), and hit 6 of its 9 3-point shots. The Aggies also had a 21-11 scoring advantage off turnovers.
Desmar Jackson had a fine game for Southern Illinois (7-4), but did not get much help. He scored 29 points, including 11 of 16 from the floor and 5 of 7 from 3-point range. Jeff Early scored 10 for Southern Illinois.