Jameis Winston -- BURGER TIME ... Before National Championship

With the BCS National Championship game tonight in L.A., Florida State QB Jameis Winston prepared his body with a solid pregame meal ... a DELICIOUS In N Out burger!!

Famous Jameis and the rest of the Seminoles spent most of their Sunday at the Rose Bowl in Pasadena, where they posed for photos, signed autographs and hung out with fans.

They also ATE like crazy ... 'cause the In-N-Out truck was on the premises handing out Double Doubles to everyone on the team.

Sources at the stadium tell TMZ Sports Jameis was very cool to everyone ... couldn't have been nicer ... and took a bag of chips to go along with his burger.