Langford scored on a 2-yard run with 24 seconds left to cap a 65-yard drive. But he ran into a crowd on a conversion attempt and the Broncos (8-2) escaped with a narrow victory.
Osweiler completed 20 of 27 passes for 250 yards with five-time MVP Manning staying back in Denver because of injuries to his foot, ribs and shoulder.
Ronnie Hillman ran for 102 yards, and the AFC West-leading Broncos (8-2) beat former coach John Fox after dropping two in a row.
Osweiler threw a 48-yard touchdown to Demaryius Thomas on Denver’s first possession and a 10-yarder to Cody Latimer early in the fourth quarter.