Only twice. The Dallas Cowboys and the Washington Redskins have played nine times on opening day between 1962 and 2010, and the Cowboys have a 6-2-1 record against their longtime rivals. The results are as follows (Dallas victories in bold):
Yes. The Cowboys have swept the home-and-away series with Washington 16 times, most recently during the 2011 season.
Accoding to Pro Football Reference, as of the start of the 2008 season, the Cowboys lead the all time regular season series against the Redskins, 56-36-2.
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The Cowboys cannot literally defeat themselves, so never.
The Redskins have defeated the Bengals 4 times and have lost 5 times. Sports Media 101 sportsmedia101.com
During the 2009 season there were two matchups between the Cowboys and Redskins. The Cowboys got the win for both games. Sports Media 101 sportsmedia101.com
The Chiefs have only beaten the Cowboys 3 times.
The Chiefs have only beaten the Cowboys 3 times.
The Cowboys lead the all-time series two games to one.
Frankly, the Dallas Cowboys have dominated their series with Washington for the past 15 years or so. But Washington has acted as a spoiler several times.
Through the 2009 season, 4-3. 2006: 0-1 2007: 1-1 2008: 1-1 2009: 2-0
Nine times. The Redskins won the first six meetings and have lost the last three.