The game was the first played in the opening round of the Old Spice Classic at Disney World. The Cowboys will take on either Butler or Washington State in the second round Friday.
There were 36 unbeaten teams remaining in major college basketball when the Thanksgiving weekend began and this game featured two of them.
Oklahoma State (6-0) raced to a 23-point lead at halftime, but that advantage was cut to four when Purdue's Kendall Stephens hit a 3-pointer with 3:18 to play.
Oklahoma State then began to expand the lead and Smart's layup with a minute remaining boosted the Cowboys in front by eight.
Markel Brown added 25 points for Oklahoma State and Le'Bryan Nash had 16.
Bryson Scott led Purdue (5-1) with 18 points.