Manning connected on 32-of-37 passes for 374 yards and has yet to throw an interception for the Broncos (3-0), who have outscored their opponents 127-71 to start the season.
Manning tossed seven scoring passes in Denver's first game and followed that up with two more in Week 2 before Monday's three-TD performance.
His favorite target was Eric Decker, who hauled down eight passes for 133 yards with a touchdown.
Wes Welker, meanwhile, made seven grabs for 84 yards and a score for the Broncos, who lost all-pro left tackle Ryan Clady for the season with a foot injury before the game.
Oakland (1-2) was led by Terrelle Pryor, who made good on 19-of-28 passes for 281 yards and a touchdown.