The Denver defense forced an Oakland three-and-out in the opening possession of the second half, giving the Broncos the ball on their own 21-yard line.
Willis McGahee got touches on three of the next four plays – two rushes and a reception — as Denver moved out to the 46-yard line.
From the 46, rookie running back Ronnie Hillman picked up the biggest gain of his career after catching a short pass and scampering down the middle of the field for 29 yards.
Two plays later, Peyton Manning hit wideout Eric Decker, who sprinted down the right sideline and into the end zone for a 17-yard touchdown. Fellow wide receiver Demaryius Thomas threw a key block on the play to clear the way for Decker.
Matt Prater kicked the extra point to make it 17-6, Broncos.
Following the touchdown drive, Manning is 22-of-27 through the air for 254 yards and two touchdowns – good for a passer rating of 130.6.
Decker has five catches for 47 yards and a touchdown, his first of the year.