Walsh made good on 24-of-38 passes, including a 6-yard TD toss to Charlie Moore that put the Cowboys (4-1, 1-1 Big 12) up 30-29 in the fourth quarter.
Ben Grogan lated added a 28-yard field goal to ice the contest for OSU, which racked up a sixth straight home win.
Walsh also ran for touchdown, as did Jeremy Smith.
Kansas State (2-3, 0-2) was paced by Daniel Sams, who passed for 181 yards with two TDs on 15-of-21 efficiency.
The Wildcats' signal-caller also rushed for 118 yards with a touchdown.
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