Julius Peppers and a swarming defense allowed only 187 yards and a single third-down conversion Thursday night, and the Bears won 16-0 to send the injury-ravaged Miami Dolphins to their second home shutout in 40 years.
Marshall drew an early flag for taunting when he flipped the ball at former Denver teammate Jay Cutler, standing in front of the Bears bench.
"We don't need that to fire us up," Chicago coach Lovie Smith said. "We were fired up when we stepped on the field."
Marshall also was penalized for an illegal block and dropped two passes before he left the game in the second quarter after aggravating a sore right hamstring. He wore street clothes on the sideline in the second half and didn't talk to reporters after the game.
Miami's already depleted offensive line lost center Cory Procter with a left knee injury. And with third-string quarterback Tyler Thigpen taking six sacks in his first NFL start since 2008, the Dolphins were no match for a Bears defense that took over the NFL lead in points allowed per game.
"Offensively we're embarrassed what we put on the field," Thigpen said. "I put the blame on me."
Playing in Miami for the first time since losing Super Bowl 41 to Indianapolis, the Bears (7-3) won for the third time in 12 days and moved a half-game ahead of Green Bay atop the NFC North.
The Dolphins (5-5) lost at home in prime time for the third time this season. Coach Tony Sparano declined to blame injuries for the dismal showing.
"Those are excuses," he said. "I'm not going to use them. I don't want my team to use them. This is the NFL. The next guy has to step up."
Peppers had three sacks and Charles Tillman recorded an interception for the Bears, who earned their first shutout since Nov. 19, 2006, against the Jets. The Dolphins were blanked for the first time since a 3-0 loss at Pittsburgh during their one-win season in 2007. Their only other home shutout since the first year of the Don Shula era came in 2001.
Matt Forte carried 25 times for 97 yards and a score for the Bears, who converted 10 of 18 third-down situations and controlled the ball for nearly 38 minutes. Cutler said the offense had an easy job.
"The way the defense is playing, we didn't have to do much," he said.
The Dolphins went 1 for 12 on third down, and a 46-yard kickoff return to start the game created their best scoring threat. They moved inside the Bears 35 for the first time on the game's final play.
Thigpen, pressed into duty after Chad Pennington and Chad Henne were hurt in Sunday's game, finished 17 for 29 for 187 yards, and he had 27 of the Dolphins' 39 yards rushing. But he found himself scrambling often and fell to 1-11 as an NFL starter.
"Offensively we couldn't get out of our own way," Thigpen said. "We would get one thing going, and then we'd get one thing to set us back."
With 2 minutes left, the crowd was down to mostly Chicago fans, and they chanted "Let's go Bears!" as the clock wound down. The chant continued after the game.
Robbie Gould put Chicago ahead 9-0 by finishing three short drives with field goals, one after the Bears' NFL-best 25th takeaway this season. A 7½-minute touchdown drive midway through the second half sealed the win, with Forte running 2 yards up the middle to score standing up on third down.
AFC sack leader Cameron Wake reached Cutler on third down in the opening period, which forced the Bears to settle for a 46-yard field goal.
The Bears got the ball back when Tillman intercepted a tipped pass, and Gould kicked a 24-yarder for a 6-0 lead.
Procter wore a brace after the game and was scheduled for an MRI exam Friday. ... The Bears' sack total was their highest since Sept. 30, 2007. ... Brown has totaled 21 yards rushing in the past two games. ... Thigpen is the 15th quarterback to start for the Dolphins since Dan Marino.
The Atlanta Falcons have agreed to a five-year contract extension with wide receiver Julio Jones. Sources say he will receive $71.25 million total, with $47.5 million guaranteed.
Randall Cobb, who fell hard on his right shoulder on the third play in Saturday's 39-26 preseason loss to the Eagles, avoided major injury but will have additional tests done Sunday.
Redskins coach Jay Gruden said he was left like everyone else -- scratching his head over how Robert Griffin III went from being cleared one day to out the next with concussion symptoms.
Dallas Cowboys wide receiver Dez Bryant will go into the regular season without having taken a snap in the preseason.
Bengals QB Andy Dalton left Saturday's 21-10 preseason win over the Bears as a precaution with a neck injury that appeared to happen on his first and only series of the night.
Baltimore Ravens wide receiver Steve Smith and Washington Redskins cornerback Chris Culliver were ejected with less than a minute left in the first quarter of Saturday night's preseason game.