Williams scored on runs of 9, 3 and 44 yards, his final score putting the Mustangs (8-2, 6-1 Big Sky) up 35-0 five minutes into the second quarter. Akaninyene Umoh, Rocky Meszaros and Ryan Solomon also scored on the ground.
With Cal Poly's conference-leading rushing offense amassing 505 yards, Broadous only had to throw the ball 14 times. His eight completions included touchdowns to Cole Stanford, Willie Tucker and Brandon Michalkiewicz, all in the first half.
Kevin Yost threw for 335 yards and two touchdowns for the Bengals (1-9, 0-7) but was intercepted three times, with Alex Hubbard returning one of them for a score.
Cal Poly tied the school single-game record of 10 touchdowns and set a new one with 10 PATs made.