The Colts held on as long as they could, but the dike finally broke, and when it did, it was a flood of points.
The Colts trailed 21-19 heading into the fourth quarter. They lost 54-19 as the Cowboys scored the fifth-most points in team history with a barrage of points in the final period.
Dallas improved to 9-3, while Indianapolis fell to 4-8-1.
The Colts had four turnovers in the fourth quarter and five for the game. The Cowboys scored 33 points in the fourth quarter, including a 38-yard scoop-and-score by ex-Colts safety Malik Hooker. (Hooker also had a first half interception.)
It was all fun and games for the Cowboys in the final stanza.
Their final three offensive scoring drives covered 53, 72 and 29 yards following two interceptions by DaRon Bland and a fumble recovery by Sam Williams.
Matt Ryan finished 21-of-37 for 233 yards with two touchdowns and three interceptions, and Jonathan Taylor ran for 82 yards on 22 carries. Ryan was sacked three times.
Dak Prescott was 20-of-30 for 170 yards, three touchdowns and an interception. CeeDee Lamb caught five passes for 71 yards and a touchdown, and Michael Gallup had four receptions for 23 yards and two touchdowns.
Tony Pollard had 12 carries for 91 yards and two touchdowns, and Ezekiel Elliott ran for 77 yards and a touchdown on 17 tries.