Prescott’s 8-yard touchdown pass to Jason Witten gave the Cowboys a 7-0 lead with 10:43 remaining until halftime.
Dallas entered Thursday’s game, having lost three games in a row while getting outscored 92-22. They had only two touchdowns playing without All-Pro running back Ezekiel Elliott in losses to the Falcons, Eagles and Chargers.
The Cowboys went three-and-out on their first four drives, with four punts, before their 11-play, 59-yard drive.
Wide receiver Jamison Crowder has killed Washington, letting a Kirk Cousins pass bounce off his hands and into the arms of safety Jeff Heath with Washington threatening at the Dallas 16. Crowder later fumbled a punt that L.P. Ladouceur recovered.