On Thursday, November 30, 2017, the Dallas Cowboys defeated the Washington Redskins, 38-14, at AT&T Stadium at Arlington, Texas. Dallas leads the overall series 70-44-2, which includes regular-season and postseason contests.
1995. The Cowboys lost to the Redskins 27-23 in Washington and 24-17 in Dallas and went on to defeat the Pittsburgh Steelers in Super Bowl XXX.
I don't know what the preseason schedule for the Cowboys was in 1960 but as far as their first ever regular season game, the Cowboys lost to the Pittsburgh Steelers, 35-28, on September 24, 1960.
Yes. On December 16, 2012, the Dallas Cowboys defeated the Steelers by the score of 27-24 in overtime.
Chicago Bears in SuperBowl XLI and the Dallas Cowboys in SuperBowl V.
1937. The Redskins defeated the Bears, 28-21, in Chicago on December 12, 1937 to win their first NFL championship.
The Dallas Cowboys won five Super Bowls, these were the teams they defeated:1/16/1972 - Miami Dolphins1/15/1978 - Denver Broncos1/31/1993 - Buffalo Bills1/30/1994 - Buffalo Bills1/28/1996 - Pittsburgh Steelers
The Dallas Cowboys played in the Divisional round of the NFC Playoffs on January 17, 2010, having defeated the Philadelphia Eagles in the Wild Card round. Unfortunately, legendary (ex-Green Bay) QB Bret Favre led the Minnesota Vikings in a resounding defeat of the Cowboys, 34-3, at the Metrodome in Minneapolis, MN.
IX - Minnesota Vikings (16-6)X - Dallas Cowboys (21-17)XIII - Dallas Cowboys (35-31)XIV - Los Angeles Rams (31-19)XL - Seattle Seahawks (21-10)XLIII - Arizona Cardinals (27-23)
1993-1994 season
The Cowboys cannot literally defeat themselves, so never.
the Redskins and Browns
No, the Cowboys would then need to defeat the winner of the New Orleans Saints-Arizona Cardinals game in the NFC Championship game on January 24 to advance to the Super Bowl.