Speaking on condition of anonymity because the team hasn’t publicly announced the switch, both people confirmed coach Vance Joseph informed his players of the QB switch at a team meeting Wednesday morning.
The move was first reported by KUSA-TV in Denver.
The Broncos (3-4) visit NFL-leading Philadelphia (7-1) on Sunday.
Siemian has two TD passes and eight interceptions over the Broncos’ 1-4 slump, including three ugly interceptions in a 29-19 loss at Kansas City on Monday night that wasted a strong defensive effort.
Peyton Manning’s former backup, Osweiler went 5-2 in Denver’s run-up to the Super Bowl 50 title, but left in free agency. After flopping in Houston last year, he was traded to Cleveland, which released him this summer.
The Broncos quickly re-signed Osweiler after backup Paxton Lynch sprained his throwing shoulder in the preseason.