Crusty French bread topped with melted cheese and sitting in a sweet onion broth…this French onion casserole is a must-serve side dish or easy vegetarian dinner for all of your cozy gatherings this season!
Table of Contents
If you enjoy French onion recipes, be sure to try this French onion chicken bake, this French onion pasta bake with spinach and mushrooms, and this dump-and-bake French onion chicken, too!
I made this yesterday and loved it! It is delicious!
– Janine
Don’t you just love a good bowl of French onion soup? This casserole takes all of those delicious flavors and bakes them into an easy dish that can be served alongside your favorite Thanksgiving turkey, cast iron filet mignon, Dutch oven pot roast, fresh seafood, pineapple glazed ham, or roast chicken.
How to Make French Onion Soup Casserole
This easy French onion soup casserole is versatile, cozy, and incredibly rich. You’ll find detailed instructions in the recipe card below, but here’s the overview:
- Cook the onions in butter for about 30 minutes. I know this may seem like a long time, but this low-and-slow process caramelizes the onions, giving your casserole the beautifully rich, French onion soup flavor. Don’t rush this step!
- Add the beef broth and the Worcestershire sauce, and bring the liquid to a boil.
- Reduce the heat and simmer, uncovered, for about 30 minutes. The broth will reduce. Remember, we’re making a casserole instead of a soup! Taste and season with salt and black pepper at this point, if desired.
- Pour the onion and broth mixture into a greased pan.
- Lightly toast the slices of bread.
- Place the toasted bread in a single layer on top of onion and broth mixture.
- Cover the bread with a thick layer of the shredded mozzarella and top with grated Parmesan.
- Bake, uncovered, until the cheese is melted and brown on top, about 20-30 minutes.
Serving Suggestions
This French onion casserole works nicely as a side dish with just about any main course, and it’s easier to prepare than individual bowls of soup. Try it with Crock Pot turkey tenderloin, a ham steak with brown sugar glaze, dump-and-bake cranberry chicken, or grilled tenderloin. It’s also a lovely meatless weeknight dinner alongside a kale apple salad or a classic Caesar salad.
This recipe was exactly what I needed to use up an abundance of onions. I had all the ingredients on hand. Thank you so much for a delicious dinner that was fun to make and enjoy. This dish is sweet and rich with simple ingredients. It doesn’t need any additional seasonings. I followed it as written. Yum!
– Stacy
Did you make this recipe?
If you enjoyed this recipe, please leave a comment with a 5-star review at the bottom of the post. Thank you!
French Onion Casserole
Ingredients
- 3 medium sweet onions, sliced
- 3 tablespoons salted butter
- 4 cups beef broth (use vegetable broth or vegetable stock for a vegetarian dish)
- 1 teaspoon Worcestershire sauce
- 4 ounces French baguette bread, sliced about ½-inch in thickness (approximately 10-12 small slices)
- 1 cup (4 ounces) shredded mozzarella cheese (or sub with Gruyere or Fontina when available)
- ¼ cup grated Parmesan cheese
- Optional garnish: chopped fresh thyme or parsley
Instructions
- Preheat the oven to 350°F. Grease a medium casserole dish (approximately 2 quarts, or about 11 x 7-inches or 9-inches square). Set aside.
- Melt the butter in a large saucepan over low heat.
- Add the onions and cover. Cook for about 30 minutes, stirring occasionally.
- Add the beef broth and the Worcestershire sauce; bring to a boil.
- Reduce the heat to low. Allow the liquid to simmer, uncovered, for about 30 minutes so that the broth reduces.
- Pour the onion and broth mixture into the prepared baking dish.
- Lightly toast the slices of bread.
- Arrange the toasted bread in a single layer on top of onion and broth mixture.
- Cover the bread with a thick layer of shredded mozzarella. Sprinkle grated Parmesan over top.
- Bake, uncovered, for 20-30 minutes, or until cheese is melted and lightly browned on top. If you prefer a darker, crispier topping, you can place the dish under the broiler for the final 1-2 minutes (just keep a close eye on it so that it doesn't burn). Garnish with chopped fresh herbs, if desired.
Notes
Nutrition
French Onion Soup Casserole Recipe Variations
- No mozzarella? You can use another good melting cheese such as gruyère cheese or Fontina. Sharp white cheddar would also be great!
- Any white crusty bread would work well for the topping. Try a homemade baguette recipe or this no-knead Dutch oven bread when you have the time!
- Use beef broth or beef stock for the most authentic flavor.
- Add meat such as chicken, ground beef, or sausage for extra protein.
- To serve a larger group, double all of the ingredients and bake the casserole in a 9 x 13-inch dish.
More Vegetable Casserole Recipes
Easy Broccoli Casserole
30 minutes mins
Green Bean Casserole with Frozen Green Beans
40 minutes mins
Spinach Casserole
40 minutes mins
This recipe was originally published in September, 2014. It was updated in November, 2024.
This looks delicious and so perfect for the cooler months ahead!
Thanks for visiting, Bianca! It really is the perfect side dish for the cooler months!
This looks great and I love how cleanup is a little easier with only 1 casserole bowl to soak and scrape instead of multiple little ones.
So true, Thao! The clean-up is MUCH easier. 🙂
Oh my word…these photos looks delicious! Heading on over to Red Lion to check it out asap!
Hi, Nicola! Thanks! 🙂
This looks awesome. Love French Onion Soup and this is a new twist. Thanks for sharing at What’d You Do This Weekend.
Linda
Thanks, Linda! And thanks very much for visiting!
I love French Onion soup, but haven’t made it because my oldest son doesn’t like onions…:-( Maybe I can make this and make him something else 🙂
Erlene, serve it on the side so that you can enjoy it…and let your oldest son eat the meat or other main course instead. Plus, I bet he’d love the bread and cheese part — even if he doesn’t love onions! 🙂
Yum, looks so good!
Thanks, Sharon!
I love the flavor of french onion soup…I know I will love this!! So glad you shared it with us at Foodie Fridays…I’m wishing I had some now!
This looks delicious! Thanks for linking up with SNF! Pinned to our party board!
Thanks so much for the pin, Jaren!
What a wonderful and tasty dish! Thanks for sharing!
Have a nice weekend!
Thanks, Mila! So glad that you stopped by. 🙂
I love French Onion Soup, so this looks incredible!!! Thank you so much for linking up at Tasty Tuesday! Your recipe has been pinned to the Tasty Tuesday Pinterest board! Please join us again this week!
This looks delicious, a great warming meal. Thanks for linking up to Sweet and Savoury Sunday, stop by and link up again. Have a great day!!
Thanks so much for visiting, Laura!
Love thie idea of getting the flavors of french onion soup in a casserole. Pinned. Thanks for bringing it by Weekend Bites.
Thanks so much for the pin, Diane! It’s definitely an easier way to accomplish the same flavors. 🙂
I know it would tast different w chic broth but don’t eat beef what do you think
Sure! I think that you can definitely make it with chicken broth. It will of course taste different, but it will still be good if you prefer chicken. 🙂
Se puede ptepsrar esta receta con bsde de sslsa nkanca???
Love the soup of this casserole! French onion soup is one of my favourite comfort foods so I can’t wait to try this!
How easy is it to serve at the table. Does anyone have pictures
I made this yesterday and loved it! It is delicioud!
Thanks, Janine! So glad that you enjoyed it!
Can this french onion soup casserole be frozen
Hi, Susan! Yes, I think that would work fine (either before or after baking). 🙂
This recipe was exactly what I needed to use up an abundance of onions. I had all the ingredients on hand. Thank you so much for a delicious dinner that was fun to make and enjoy. This dish is sweet and rich with simple ingredients. It doesn’t need any additional seasonings. I followed it as written. Yum!
Yay! So glad that it was a hit, Stacy! Thanks for letting me know. 🙂
Excellent soup and easy to make! Great for the winter.
Thanks, Robin!