Grayson scored on runs of 2 and 81 yards for the Mustangs (4-1), who finished with 287 yards rushing.
Dally ran for 33 yards, including a 1-yard TD run. He also completed 11 of 18 passes for 132 yards and a 34-yard touchdown to Ramses Barden that made it 27-7 with 11:03 left in the third quarter. The Jackrabbits (3-3) never got closer than 13 points the rest of the way.
The Mustangs sacked SDSU quarterback Ryan Berry four times and held the Jackrabbits to just 38 yards rushing.
Berry completed 19 of 33 passes for 252 yards and three touchdowns. He also was intercepted twice by Greg Francis.
Fox caught eight passes for 113 yards and Harris had eight catches for 95 yards.
Dally's short TD run with 2:33 left in the second quarter gave the Mustangs a 20-7 lead at the half.
Cal Poly finished with 419 yards, while SDSU managed 290.