Jefferson ran for two long gains off direct snaps and Stewart had a 51-yard touchdown scamper in the second half as KSU proved incapable of stopping the Buffs' running game most of the afternoon.
Stewart also completed his first touchdown pass in the second quarter executing a halfback pass and finding Toney Clemons in the end zone.
It was the final Big 12 Conference game ever in Boulder.
McKnight's two touchdown catches (21st and 22nd) made him the career record holder for touchdown receptions at CU.
Kansas State got out to an early 14-3 lead, but the Buffs rebounded, sticking to the game plan to run the ball. Defenders such as Jimmy Smith, B.J. Beatty and Josh Hartigan came up with big plays throughout the day.
Hartigan racked up three sacks as the Buffs put KSU quarterbacks on the ground six times in the game. They have 15 sacks in the past two weeks.
Colorado is 5-6 overall and 2-5 in Big 12 play and needs a win to become bowl eligible and extend its season and the tenure of its current coaching staff.
Nebraska needs a win to assure itself of a north division championship and a trip to the Big 12 title game.