Stewart shot 6-for-10 from the field and Gordon went 7-for-12 as the Bulldogs (3-1), playing on the road for the first time this season, led for all but the opening minute and by double-digits most of the game.
On Friday they'll play Southern Illinois, which routed Chattanooga 63-41 later Thursday.
UC Irvine (2-2) plays Chattanooga.
The Anteaters pulled within five early in the second half, but Charles Rhodes took Mississippi State back to a double-digit lead 51-40 with a three-point play.
Rhodes had 11 points and 11 rebounds.
A driving layup from Ben Hansbrough then completed a 14-4 run that put the Bulldogs up, 55-40, with 12:47 remaining.
It was the first of three 15-point leads for the Bulldogs, and Irvine got no closer than nine the rest of the game.
Hansbrough, the younger brother of North Carolina star Tyler Hansbrough, had 13 points.
Mississippi State opened the game with a 16-8 lead that included 7 points from Gordon on a pair of lay-ups and a banked-in 3-pointer.
Hansbrough gave the Bulldogs a 29-18 lead with a 3-pointer, and returned the lead to double digits with another 3.
The Anteaters cut the lead to 41-34 with a 10-7 run in the final three minutes of the half.
Gordon and Stewart had 11 apiece in the first half for the Bulldogs, who shot 57 percent in the half.