Vaz, a junior quarterback filling in for injured starter Sean Mannion, amassed 332 yards on 20-of-32 passing for the Beavers, who moved to 5-0 for the first time since 1939.
Oregon State racked up 450 yards of total offense with the help of Markus Wheaton, who made five grabs for 66 yards with two touchdowns.
Brandin Cooks chipped in with 173 receiving yards on eight catches, while Storm Woods rushed for 57 yards and a touchdown in the win.
Riley Nelson was picked off three times for the Cougars (4-3), throwing for 305 yards with a touchdown.
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