Gregg closed his career with the Dallas Cowboys, as did his Packer teammate, cornerback Herb Adderley. They both helped the Cowboys win Super Bowl VI in January 1972, making them the only players (along with former teammate Fuzzy Thurston, who was on the Baltimore Colts NFL championship team in 1958 and Tom Brady of the New England Patriots) in professional football history to play on six NFL title teams. Gregg wore the number 75 for 15 seasons in Green Bay, but that number belonged to Jethro Pugh in Dallas, so Gregg wore number 79 for his final season in 1971.