Marcus Smart added 25 points and grabbed nine rebounds for the Cowboys (15-5, 5-3 Big 12), who notched their first win in Lawrence since 1989.
It was also Oklahoma State's first win away from home this season season and the Cowboys' first road victory over a Top 5 team since 1958.
The Jayhawks (19-2, 7-1), meanwhile, had their 18-game overall winning streak snapped.
Ben McLemore led Kansas with 23 points.
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