Dan Graziano of ESPN.com first passed along word of the QB change Tuesday.
Osweiler started his NFL career as a second-round selection of the Broncos in the 2012 draft and spent his first four years with the franchise. He returned in early September after the Cleveland Browns released him, and he took back the reins of the offense in Week 9.
Although the 26-year-old Arizona State product showed signs of promise during his first stint in Denver, he struggled during the 2016 campaign with the Houston Texans.
He completed just 59 percent of his throws for 2,957 yards with 15 touchdowns and 16 interceptions across 15 appearances after signing a four-year, $72 million contract with $37 million guaranteed.
The Texans traded him to the Browns in what amounted to a salary dump in March, but Osweiler never lost his confidence during the whirlwind stretch.
"Absolutely," he told reporters in May when asked whether he's a starting-caliber QB. "I think the proof is in the film for the past two years."
His grip on the Broncos job was always tenuous this time around, though. Head coach Vance Joseph made the lack of guaranteed opportunities clear after inserting him in the lineup over Trevor Siemian.
"Brock plays well, he plays next week," he said. "It's very simple."
Osweiler failed to secure the starting spot as he completed 53 percent of his throws with three touchdowns and four interceptions across four appearances (0-3 as the starter).
Denver is switching to Lynch as a last-ditch effort to find an offensive spark. He missed the first half of the 2017 regular season with a shoulder injury, which is why the Broncos signed Osweiler and gave him the first chance to replace Siemian while the Texas native recovered.
The Broncos grabbed Lynch in the first round of the 2016 draft. He didn't play much as a rookie, connecting on 59 percent of his throws with two touchdowns and one pick in three appearances. So Sunday is a key opportunity for him to show he could become the team's quarterback of the future.