In a large skillet, brown the bratwurst sausages on all sides over medium-high heat.
Add the sliced onion and minced garlic to the skillet and cook until softened.
Pour in the Oktoberfest beer and bring to a simmer. Cover and let the sausages braise for about 20 minutes.
Remove the sausages from the skillet and set aside. Reserve the beer-braised onions for later.
In a separate skillet, melt butter over medium heat. Place a slice of rye bread in the skillet and top with a slice of Swiss cheese.
Slice the bratwurst sausages and place on top of the cheese. Add some of the beer-braised onions on top.
Top with another slice of Swiss cheese and another slice of rye bread.
Cook the grilled cheese sandwich until the bread is golden brown and the cheese is melted, flipping halfway through.
Repeat with the remaining ingredients to make 3 more sandwiches.
Serve the Oktoberfest Beer-Braised Brat Grilled Cheese with mustard and sauerkraut on the side. Enjoy!
