Only seven Tigers played more than 5 minutes in the game and Denmon paced a balanced scoring effort with 17 points.
Missouri has won six in a row and is tied with Kansas for the lead in the Big 12 Conference race.
Ricardo Ratliffe added 15 points and 12 rebounds for the Tigers (24-2, 11-2 Big 12). Phil Pressey and Kim English each had 13.
The Tigers held Oklahoma State to two points during a stretch of 7:59 in the first half en route to a 22-point lead at intermission.
The Cowboys (12-14, 5-8) got 23 points from Keiton Page. It was Oklahoma State's fourth loss in six games.