McLemore hauled down six rebounds. Withey supplied 14 points and 10 boards.
Elijah Johnson (13 points) and Travis Releford donated (11) also reached double figures for the Jayhawks (10-1), who reeled off their the ninth straight win.
The Buckeyes (9-2), meanwhile, saw their 39-game home winning streak against non-conference foes snapped.
Deshaun Thomas scored 16 points and Shannon Scott contributed 15 off the bench for Ohio State.