Miami wins the Super Bowl. Shake calls off the wedding because Barbara Jane doesn't get "it". When she realizes that Billy Clyde didn't get "it" either, they get together.
Billy Clyde Puckett (Burt Reynolds) and Marvin "Shake" Tiller (Kris Kristofferson) are teammates on Miami's professional football team (the nickname is never revealed), owned by Big Ed Bookman (Robert Preston). The early scenes of the movie shows the team are a bunch of big kids who are always getting in trouble, sleeping with their fans, and getting bailed out by Big Ed. Billy Clyde and Shake are also roommates in a condo, and Big Ed's daughter Barbara Jane (Jill Clayburgh) is also a roommate of theirs, but she has a platonic relationship with them going back to their days in college. Barbara Jane returns from a trip to Africa just as Miami is about to go into the playoffs. Soon after, Barbara Jane and Shake begin a romantic relationship after Shake reveals to both her and Billy Clyde that he is more self-confident since he attended a self-improvement seminar called B.E.A.T., led by Friedrich Bismark (Bert Convy). He attended it while she was gone, and he knows it worked because he gets "it", and as a result, he has not dropped a pass since. Days later, they get engaged to be married, even though Barbara Jane has been married and divorced twice already and has a history of rushing into relationships.
As the team advances in the playoffs, Barbara Jane wants to know what Shake is talking about when he says that B.E.A.T. helped him get "it", since she is not a follower. Shake has told her that he cannot describe "it" since it's means different things to different people, so she enrolls in a B.E.A.T. seminar.
Meanwhile, Billy Clyde, who has feelings for Barbara Jane himself, also enrolls in the seminar so he knows what she is going through. Since Miami won the conference championship and will play in the Super Bowl, the team has a week off to allow both of them to do the seminar right away. Barbara Jane also tells Shake that she wants the wedding to happen right after the game. The seminar lasts 48 continuous hours, and Bismark won't allow a break, not even for the restroom. Billy Clyde gets around that by taping a flask to his leg with a hose running from it to his...do I really need to tell you where? After the seminar ends, Barbara Jane is exhausted, but also guilty that she didn't get "it". Billy Clyde, also exhausted, says that he got "it", and now understands Shake.
The team is now playing in the Super Bowl, and playing poorly. Billy Clyde, speaking like Bismark, says that he is choosing to win the game, and both he and Shake pretty much single-handedly win the game for Miami. Now at the wedding, Shake is having second thoughts about marrying Barbara Jane because she still doesn't get "it". Earlier, Bismark told him that "mixed marriages" don't work, and Shake is afraid that this marriage will fail and ruin their friendship. Billy Clyde, Shake's best man, tells him to forget "it" because all that matters is that they love each other. At the altar, Barbara Jane says I do, but Shake says I don't. He just can't bring himself to marrying someone who doesn't get "it" and calls off the wedding. Big Ed immediately tells Shake his days with Miami are over, and the church erupts in a huge brawl. Billy Clyde pulls Barbara Jane away from the chaos and admits to her that he has been lying all this time and never got "it" either. A relieved Barbara Jane hugs Billy Clyde and they leave the church.
The movie ends with Billy Clyde and Barbara Jane, still in their tuxedo and wedding dress, walking down Miami Beach. She says that she is officially breaking up with Shake and wants to be with Billy Clyde. He reveals his feelings for her as well, and they continue to walk down the beach deciding what to do next.