Nash got four of his points during a 7-1 spurt at the end of the first half that effectively sealed the victory as the Cowboys (9-1) won a second straight.
Marcus Smart and Markel Brown each added 13 points. Kamari Murphy also reached double figures with 10 points off the bench for Oklahoma State.
The Bulldogs (8-3) were led by Chris Anderson's 14 points and eight rebounds.
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