The Cornhusker coach, Moe Iba, used nine players and got a total of 31 points from his reserves. Nebraska made 25 of 31 free throws, 20 of 24 in the second half. A stifling man-to-man defense led by Greg Downing held Missouri's high-scoring Ricky Frazier to just 6 points, equaling Frazier's season low. Downing also was the leading Nebraska scorer with 14 points.

Missouri had beaten Nebraska once this season, 44-42. ''I can't say if Nebraska is better than Missouri,'' said Iba, ''but our kids knew they could win because they should have won at Lincoln. This is as big a win as any in Nebraska history.'' Virginia Continues to Roll

In other games Saturday, Virginia defeated Virginia Tech, 80-66, prompting Charlie Moir, the Tech coach, to say: ''Virginia is the No.1 team in the nation.'' Virginia (22-1), ranked third and fourth in the polls, completed a week in which the Cavaliers also beat North Carolina, ranked No.2 in the polls, and had taken over first place in the Atlantic Coast Conference.

In the nonleague victory over Virginia Tech, Ralph Sampson paced the Cavaliers with 25 points, 21 rebounds and seven blocked shots. In the Southwest Conference, Arkansas remained on top with a 62-55 overtime victory over Texas in Fayetteville, Ark. Darrell Walker, an Arkansas junior, was ejected with 18 seconds left in the overtime period after punching Ray Harper, a Texas sophomore, in a replay of a confrontation last season, when Walker was also ejected.

Doug Smith, Texas's assistant sports information director, was punched in the stomach as he walked with the Texas coach, Abe Lemons, to the locker room, causing Lemons to remark that the incidents ''ruined a good ball game.'' ''How many times has Darrell Walker hit somebody?'' said Lemons. ''It the leag ue doesn't suspend him, they have no guts.'' Walker said he hit Harper because ''he came at me. Harper is alwaysdoing things to me that no one sees. He elbows me and runs into me and calls me all kinds of names. I hit him once just to get him off me.''