How many winning Super Bowl quarterbacks were Heisman Trophy winners?

Jim Plunkett, Oakland Raiders and Stanford

The last Heisman winning QB that started and won a Super Bowl was Jim Plunkett who won the Heisman in 1970 (Stanford) and won Super Bowls XV and XVIII with the Raiders.

The only other Heisman winning QB to start and win a Super Bowl was Roger Staubach who won the Heisman in 1963 (Navy) and won Super Bowls VI and XII with the Cowboys.