Rookie quarterback Andy Dalton marched the Bengals from their own 5-yard line in a last-chance shot at the victory as time was winding down, getting as far as Denver's 48-yard line.
But then the Broncos' defense stiffened, sacking Dalton on second-and-10 and forcing him to miss on two desperation pass attempts in the final seconds.
Orton finished 15-of-25 for 195 yards and found Eric Decker on a 52-yard scoring strike early in the fourth quarter for a 24-15 lead.
Decker made five catches for 113 yards and two scores, while Willis McGahee ran the 28 times for 101 yards and a TD for the Broncos (1-1).
Dalton ended with 332 yards and two touchdowns on 27-of-41 passing for the Bengals (1-1).