November 28th, 1974 - Dallas 24 Washington 23.
For those that don't know... are too damn young to recall the Mad Bomber... Sucker Puncher*:
From Cowboys-Deadskins Rivalry:
On November 28, 1974, the Redskins were 8-3 and ready to secure a playoff berth with a win against the Cowboys (6-5) in a nationally televised game in Dallas. With less than ten minutes to go in the third quarter, Washington was leading 16-3, when Redskins linebacker Dave Robinson knocked Roger Staubach out of the game. Rookie Clint Longley led the Cowboys to a last-minute come-from-behind victory, throwing a 50-yard touchdown pass to Drew Pearson with 28 seconds left. The final score was Cowboys 24, Redskins 23.
The Redskins were stunned. "I don't have very much to say," coach George Allen said when it was over. "It was probably the toughest loss we ever had."
* http://dy.snimg.com/story-image/4/6/4545426/195465-0-600.jpg
Ahhh yes, the Clint Longley game.
LOL...I was a diehard young teen Redskins fan that day...it was a black day on my soul for many years!