Junior quarterback Jake Maier threw for three touchdowns and ran for another as the Aggies piled up 46 second-half points to erase a 21-3 deficit.
By the end Maier completed 36 of 48 passes for 292 yards, shaking off a first half in which a raucous Washington-Grizzly Stadium and Grizzlies quarterback Dalton Sneed had the Aggies on their heels.
It was the third straight game in which UC Davis (7-1, 5-0 Big Sky Conference) erased a two-score deficit: they trailed Idaho State 30-14 and Cal Poly 10-0 before winning both games.
It was the third straight loss for Montana (4-4, 2-3).
"We don't quit," said UC Davis receiver Keelan Doss, who caught 10 passes for 78 yards and a touchdown. "Going into halftime we knew we had to make some adjustments and I felt we did that. We just talked about how we weren't playing our best and we had to get used to that crowd."
The Aggies were undone by several false starts and were flagged three times for unsportsmanlike conduct on one first-half drive. After Samuel Akem caught his second scoring pass from Sneed with 50 seconds left in the half, Montana led 21-3.
UC Davis turned it around behind Maier, whose final TD pass, covering 2 yards to Carson Crawford, was the Aggies' fifth touchdown of the fourth quarter.
It was a shocking reversal given Montana led 21-6 and was driving late in the third quarter before giving up the ball on downs at the UC Davis 34-yard line.
The Aggies quickly used a 56-yard double pass from Crawford to Wesley Preece to set up their first TD, a 5-yard strike from Maier to Preece. That cut Montana's lead to 21-13 at the 2:17 mark.
"I think everybody had a lot of confidence that we were going to get back on track," UC Davis coach Dan Hawkins said. "That was a huge momentum shift for us. You guys have seen enough football to know momentum is a deadly force, it really is. Once we got it going, our guys were able to throw a rock on the gas pedal and keep it going."
The Aggies drew even when Maier hit Doss with a 4-yard touchdown pass and then Ulonzo Gilliam for the 2-point conversion with 13:31 left in the game.
After a Montana punt, Tehran Thomas tore off a 56-yard touchdown run to put the Aggies ahead 28-21 with 10:59 left.
Gilliam and Maier added short scoring runs to make it 42-21 with 7:42 remaining in the game.
Sneed's strong first half included several scrambles and scoring passes covering 13 and 14 yards to Akem. In between, Jeremy Colhoun had a 15-yard scoring run for the Grizzlies.
"We showed how well can play in the first half," Montana coach Bobby Hauck said. "The second half was probably a little bit the other side of the coin from that, not to discredit UC Davis. I'm disappointed we couldn't sustain that the second half. And when it started to go the wrong direction we didn't get it turned around."
Sneed threw for 230 yards, 171 in the first half. He ended up with three interceptions and a fumble. Akem had nine catches for 75 yards. Calhoun had 16 carries for 73 yards for the Grizzlies.
UC Davis: The Aggies ranked No. 6 in the Football Championship Subdivision, rolled up 406 yards of offense and scored 46 points after halftime.
Montana: The Grizzlies cruised to a 21-3 halftime lead and then faltered. Three second-half turnovers helped seal their third straight defeat.
UC Davis: The Aggies return home to face Big Sky foe Northern Arizona on Nov. 3.
Montana: The Grizzlies start a two-game road swing with a league game at Southern Utah on Nov. 3.
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