Fluffy Oven-Baked French Onion Soup Casserole

Fluffy Oven-Baked French Onion Soup Casserole

French Onion Soup Casserole is a comforting and hearty twist on the classic French onion soup. This dish combines all the rich flavors of caramelized onions and melted cheese, but in a convenient casserole form, making it perfect for family dinners or potlucks. The best part is that it’s baked in the oven, allowing the flavors to meld beautifully while requiring minimal stovetop effort.


– 6 large onions, thinly sliced
– 3 tablespoons butter
– 2 tablespoons olive oil
– 3 cloves garlic, minced
– 1 teaspoon sugar
– 1 teaspoon dried thyme
– 1/2 cup dry white wine (optional)
– 4 cups beef broth
– 2 cups chicken broth
– 1 tablespoon Worcestershire sauce
– Salt and pepper to taste
– 1 whole French baguette, sliced into 1-inch thick rounds
– 3 cups shredded Gruyère cheese


1. Preheat your oven to 375°F (190°C).

2. Caramelize the onions: In a large skillet or Dutch oven, melt the butter and olive oil over medium heat. Add the sliced onions and cook, stirring frequently, until they are soft and golden brown, about 25-30 minutes. Sprinkle with sugar during cooking to enhance caramelization.

3. Add garlic and thyme: Stir in the minced garlic and dried thyme, and cook for another 2-3 minutes until fragrant.

4. Deglaze and simmer: Pour in the white wine (if using) to deglaze the pan, scraping up any browned bits from the bottom. Cook for a few minutes until the liquid reduces. Add the beef broth, chicken broth, and Worcestershire sauce. Bring the mixture to a simmer and let it cook for 10-15 minutes. Season with salt and pepper to taste.

5. Assemble the casserole: In a large casserole dish, layer half of the baguette slices to cover the bottom. Pour half of the onion mixture over the bread, spreading it evenly. Sprinkle half of the shredded Gruyère cheese over the onions. Repeat the layers with the remaining bread, onions, and cheese.

6. Bake: Cover the casserole dish with aluminum foil and bake in the preheated oven for 25 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown on top.

7. Serve: Let the casserole cool for a few minutes before serving. Enjoy this comforting dish with a side salad or a crusty piece of bread.

Bon appétit!