Jump to RecipeJump to VideoLeave a ReviewPin Recipe

Disclosure: This post may contain affiliate links. I may earn a small commission for my endorsement, recommendation, testimonial, and/or link to any products or services from this website.

Crusty French bread topped with melted cheese and sitting in a sweet onion broth…this French Onion Soup Casserole is a must-serve side dish or easy vegetarian dinner for all of your cozy gatherings this season!

Overhead shot of an easy French Onion Soup Casserole in a white baking dish

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 roasted turkey, grilled steak, pot roast, fresh seafood, or baked chicken.

It pairs beautifully with just about any main course, it’s easier to prepare than individual bowls of soup, and the rich broth base you cannot beat!

A close up of a french onion soup casserole

Add Chicken, Sausage or Beef!

If you want to make this dinner a true one-dish meal, you can add cooked chicken, sausage, or ground beef into the soup base when you transfer the mixture to the baking pan.

It’s also a lovely vegetarian main course option with a salad alongside for some leafy green freshness!

An overhead shot of a French onion soup casserole in a white dish topped with bread and cheese

Prepare this Casserole in Advance

While the cook time is longer than my normal quick-prep recipe, it’s super easy and it only requires about 10 minutes of actual hands-on time.

I like to prep the French Onion Soup base for the casserole in advance (up to a day or two ahead of time), so that when I need to pop it in the oven on a busy weeknight everything is ready to go!

How to Make French Onion Soup Casserole

  1. Melt butter in a large saucepan over low heat.
  2. Add onions and cover. Cook for about 30 minutes, stirring occasionally.
  3. Add the beef broth and the Worcestershire sauce. Heat the broth mixture until it boils.
  4. Reduce heat to low. Allow to simmer, uncovered, for about 30 minutes. The broth will reduce.
  5. Pour onion and broth mixture into a medium greased casserole dish (you can use a 1 ½-quart baking dish, an 11×7-inch baking dish, a 9-inch square baking dish, or something similar in size). Lightly toast the slices of bread.
  6. Place toasted bread in a single layer on top of onion/broth mixture.
    Cover bread with a thick layer of the shredded mozzarella and top with grated Parmesan.
  7. Bake, uncovered, in a 350F oven for 20-30 minutes, or until cheese is melted and brown on top.

A side shot of a french onion soup casserole in a white dish sitting on a napkin

I hope that you enjoy this versatile, cozy, and incredibly rich dish just as much as my family does!

Top Tips for Making French Onion Soup Casserole

  • Cooking the onions for 30 minutes may seem long but this is what gives your casserole the beautifully rich, French onion soup flavor so don’t rush this step.
  • No mozzarella? You can use another good melting cheese such as gruyere or fontina. You could also use white sharp cheddar.
  • Any white crusty bread would work well for the topping.
  • I recommend using beef broth for an authentic flavor.
  • You can add meat such as chicken or sausage for extra protein.
  • You can easily prep this dish in advance, see notes below!

A French onion soup casserole in a white dish topped with cheese

More Delicious Casseroles You Might Like:

French Onion Soup Casserole

5 from 4 votes
Prep: 10 minutes
Cook: 1 hour 30 minutes
Total: 1 hour 40 minutes
Servings 6 servings
Calories 201.2 kcal
Crusty French bread topped with melted cheese and sitting in a sweet onion broth...this French Onion Soup Casserole is a must-serve side dish or easy vegetarian dinner for all of your cozy gatherings this season!

Ingredients
  

  • 3 medium sweet onions, sliced
  • 3 tablespoons butter
  • 4 cups beef broth
  • 1 teaspoon Worcestershire sauce
  • 4 oz French baguette bread, sliced about ½-inch in thickness (approximately 10-12 small slices)
  • 1 cup (4 ounces) shredded mozzarella cheese
  • ¼ cup grated Parmesan cheese

Instructions

  • Melt butter in a large saucepan over low heat.
  • Add onions and cover. Cook for about 30 minutes, stirring occasionally.
  • Add the beef broth and the Worcestershire sauce. Heat the broth mixture until it boils.
  • Reduce heat to low. Allow to simmer, uncovered, for about 30 minutes. The broth will reduce.
  • Pour onion and broth mixture into a medium greased casserole dish (you can use a 1 ½-quart baking dish, an 11x7-inch baking dish, a 9-inch square baking dish, or something similar in size).
  • Lightly toast the slices of bread.
  • Place toasted bread in a single layer on top of onion/broth mixture.
  • Cover bread with a thick layer of the shredded mozzarella and top with grated Parmesan.
  • Bake, uncovered, in a 350 degree oven for 20-30 minutes, or until cheese is melted and brown on top.

Notes

Want to Prep Ahead? Prepare the French Onion Soup base for the casserole (through Step 5) up to a day or two in advance. Keep it covered in the refrigerator until you're ready to bake it. Before baking, allow the dish to sit on the counter for about 30 minutes so that it has time to come to room temp before you put it in the oven.
I also like to toast the bread in advance. Allow the toast to cool completely and then just store it in a zip-top bag on the counter until you're ready to bake the casserole. While the oven preheats, you can add the toast and cheese to the top of the dish and then just pop it in the oven. No last-minute scurrying around the kitchen!

Nutrition

Serving: 1/6 of the recipeCalories: 201.2kcalCarbohydrates: 16.1gProtein: 10.4gFat: 9.5gSaturated Fat: 4.2gPolyunsaturated Fat: 0.3gMonounsaturated Fat: 3gCholesterol: 31.5mgSodium: 624.8mgPotassium: 108.4mg
Keyword: French Onion Soup, French Onion Soup Casserole, Onion Casserole
Course: Main Course
Cuisine: American
Author: Blair Lonergan
blair

Hey, I’m Blair!

Welcome to my farmhouse kitchen in the foothills of Virginia’s Blue Ridge Mountains. Inspired by local traditions and seasonal fare, you’ll find plenty of easy, comforting recipes that bring your family together around the table. It’s down-home, country-style cooking!

Read More

Square overhead shot of hands serving a chicken pot pie recipe with biscuits
Overhead image of a bowl of chili mac on a dinner table with cornbread
Hands serving a platter of sheet pan sausage and potatoes

Leave a Comment

Your email address will not be published. Required fields are marked *

Recipe Rating




This site uses Akismet to reduce spam. Learn how your comment data is processed.

Comments

  1. 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.

  2. This looks awesome. Love French Onion Soup and this is a new twist. Thanks for sharing at What’d You Do This Weekend.

    Linda

  3. 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 🙂

    1. 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! 🙂

  4. 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!

  5. 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!

  6. 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!!

  7. Love thie idea of getting the flavors of french onion soup in a casserole. Pinned. Thanks for bringing it by Weekend Bites.

    1. 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. 🙂

  8. 5 stars
    Love the soup of this casserole! French onion soup is one of my favourite comfort foods so I can’t wait to try this!

  9. 5 stars
    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!