Quinn had a mostly solid performance, throwing a touchdown pass but also an interception, and Tebow had a sack and a big scramble in cleanup duty.
The game was marred by an injury to Bills running back Johnny White, who was strapped to a body board and carted off the field after his head was driven into the grass on a clean tackle by linebacker Mario Haggan in the third quarter.
White moved his left hand as he was taken up the tunnel, then was taken via ambulance to a hospital. There was no immediate word on his condition.
Haggan later went to the locker room with an injured right shoulder and didn't return.
After Orton completed 10 of 13 passes for 135 yards and a touchdown, Quinn came in and had an up-and-down performance with the second-stringers, completing 10 of 16 passes for 130 yards, one TD and one interception in the end zone just before halftime.
Tebow was 1 for 2 for 10 yards with a sack. He ran once for 7 yards.
Orton's sharpness was in stark contrast to his 2-for-6 performance that led to a field goal in the starters' only series last week at Dallas.
"That was the challenge for them, to make sure we moved it better and scored more touchdowns," said John Fox, who made his home coaching debut.
Quinn drove Denver to the Bills 3 in the waning seconds of the first half, but his throw to Eric Decker was deflected by defensive end Spencer Johnson and scooped up by cornerback Terrence McGee before it hit the grass. He rumbled to midfield as time expired.
"I am not too pleased with my play," McGee said, "but luckily we were able to get that stop."
Newly signed running back Willis McGahee scored both of Denver's touchdowns when the starters were on the field. He followed a block from rookie tackle Orlando Franklin for a 1-yard TD run in the first quarter and hauled in a short pass in the right flat before outracing linebacker Reggie Torbor to the end zone for a 13-yard TD that made it 14-3 and ended the starters' night.
The Bills, who recorded nine sacks at Chicago last week, were hoping to get some pass rush on Orton without Shawne Merriman, who sat out with a minor knee injury.
Marcell Dareus, the third pick in the draft, was the only Buffalo player to get to Orton, dropping him for a 5-yard loss on Denver's opening drive.
The Broncos elected not to select a run-stuffer in a draft that was deep in defensive tackles, and earlier in the week they lost Ty Warren (triceps), their top free agent signing, and Marcus Thomas (chest) in the same practice.
So, Kevin Vickerson and Brodrick Bunkley got the starts. Bunkley had a couple of noteworthy plays, flattening Fitzpatrick in the first quarter and deflecting a pass from Fitzpatrick in the second that he nearly chased down for a pick-six.
Broncos rookie safety Rahim Moore's hit on Donald Jones sparked a short scuffle and left the Bills' wide receiver on the ground for several minutes before he got to his feet and walked to the locker room in the second quarter.
Jones had beaten Cassius Vaughn down the Bills' sideline, but Fitzpatrick's throw overshot Jones, and Moore sliced in and hit the defenseless receiver under the chin. The back of Jones' head hit the ground, and Moore was flagged for a personal foul.
Broncos S David Bruton sustained a head injury in the fourth quarter. ... Fox is the 14th coach in Broncos history.