At the funeral of their German-born grandfather Johann von Wolfhausen, brothers Jan and Todd Wolfhouse discover that family tradition demands they travel to Munich during Oktoberfest to spread his ashes on the Theresienwiese.

Their great-grandmother, Gam Gam, gives them two tickets to Munich, where a Mr. Schniedelwichsen will take them to the family resting place. While waiting for Schniedelwichsen after their arrival, the brothers unintentionally start a brawl that takes down an entire Oktoberfest tent.

Schniedelwichsen leads Jan and Todd to Beerfest, an underground drinking game tournament run by Baron Wolfgang von Wolfhausen. The triumphant German national team is furious that Schniedelwichsen would bring outsiders to the contest, so he is shot. Jan and Todd discover that the von Wolfhausens are related to the Wolfhouses. The German team reveals that Johann was a stable boy who stole the recipe for "the greatest beer in all the world" decades ago and ran away with his prostitute mother, Gam Gam. The Germans celebrate an easy win over Jan and Todd in a drinking contest by urging the audience to pelt Jan and Todd with vegetables, destroying the urn containing their grandfather's ashes, and spilling them all over the brothers.

Swearing to get revenge on the Germans, Jan and Todd return to Colorado, where they recruit college drinking friends for an American Beerfest team.