Rams star receiver Cooper Kupp ran an option route, and he and Matthew Stafford didn’t appear to be on the same page.
Stafford threw the ball straight to cornerback DaRon Bland, who returned it 30 yards for a touchdown.
The Cowboys had a 17-3 after the first quarter.
It was Bland’s third interception return for a touchdown this season. Marcus Peters in 2019 is the last player to score three touchdowns on interception returns, and the NFL record is four.
It was Stafford’s 30th career pick-six, putting him alone in second place all time. Only Brett Favre, with 32, has more in NFL history.
The Cowboys added to their lead with 13:39 left in the second quarter on a blocked punt by Sam Williams. The ball went out of the end zone for a safety.
The Cowboys’ other points came on a touchdown on an 18-yard pass from Dak Prescott to Jake Ferguson and a 58-yard field goal from Brandon Aubrey.