The Cowboys rallied from an 11-point halftime deficit to knock off the Jayhawks, led by 18 points from senior Le'Bryan Nash.
After a Jamari Traylor jumper cut the Cowboys' lead to 63-61 with 3:59 remaining, the Jayhawks would score only one point the rest of the game (a free throw by Frank Mason III). In that span, KU missed three free throws and were 0-for-6 from the floor.
Kansas shot 10-of-20 from three for the game and edged Oklahoma State in rebounds, 35 to 34, but committed 18 turnovers, including two crucial ones in the final three minutes.
Hickey finished with 15 points for the Cowboys, while Forte scored 13 and Jeff Newberry added 10. Between Saturday and Kansas' 67-57 victory over Oklahoma State in January, the Cowboys received only seven points combined from their bench.
The loss is only the Jayhawks' second in Big 12 play and snaps their five-game winning streak. Their other Big 12 loss came in January to Iowa State, whom they hold a one-game lead on in the conference standings.
Oklahoma State now owns Big 12 wins over Kansas, Baylor, Texas (twice) and Texas Tech, and has won three of its last four games. The Cowboys have a quick turnaround with a Monday night matchup against Baylor in Waco.