Maybe only the Michigan-Michigan State rivalry equals the deep devotion people can have regarding the two most famous Frankenmuth restaurants-the Bavarian-themed and appropriately named Bavarian Inn Restaurant or the Mount Vernon-inspired Zehnder's of Frankenmuth. Both amazing restaurants offer tasty family-style check dinners, yummy deserts, and ground floor shops filled with baked goods, Michigan wine, and knickknacks.
If you are committed to one or the other, I HIGHLY recommend making reservations. Lines can be long, and on an empty stomach, not fun.
For those with more flexible arrangements I would also recommend the Frankenmuth Brewery (425 S Main St, Frankenmuth, MI 48734, http://www.frankenmuthbrewery.com/) or Sullivan's Black Forest Brew Haus & Grill (281 Heinlein Strasse, Frankenmuth, MI 48734, http://www.blackforestbrewhaus.net/).
Bavarian Inn Restaurant
613 S Main St, Frankenmuth, MI 48734
Zehnder's of Frankenmuth
730 S Main St, Frankenmuth, MI 48734