Updated
French Onion Soup Casserole is the perfect combination of a classic soup and an easy casserole recipe. I love that you get all the delicious flavors from the caramelized onions, crunchy baguette, and gooey cheese in an easy-to-make weeknight dinner!
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“This is a great recipe! If my family had their way, I would make it every day” – Chelsea
Easy French Onion Soup Casserole
French onion soup has always been one of my favorites—it’s such a classic for a reason. That slightly sweet, deeply savory flavor topped with golden croutons and melty cheese? I can never resist.
And since I’m all about easy, comforting meals, it only made sense for me to turn those flavors into a casserole. This French Onion Soup Casserole has all the goodness of the soup—caramelized onions, crispy baguette slices, and plenty of gooey cheese—without needing a bowl or hours in the kitchen.
It’s rich, cozy, and just as satisfying as the classic, but way easier to make on a busy weeknight.
French Onion Soup Casserole
Equipment
- 9×13 Baking Pan
- Baking Sheet
Ingredients
- 16 oz. baguette cut into ¼-inch slices (1 loaf)
- ¼ cup unsalted butter (½ stick)
- 2 Vidalia onions halved and cut top-to-bottom into ¼-inch-slices
- 3 yellow onions halved and cut top-to-bottom into ¼-inch-slices
- 1 tsp kosher salt
- ½ tsp freshly ground black pepper
- 5 fresh thyme sprigs leaves removed
- 1 bay leaf
- ½ cup dry sherry
- 1 cup unsalted beef broth
- 2 cups unsalted chicken broth
- 8 oz. freshly shredded Gruyere cheese (about 2 cups)
Video
Instructions
- Preheat oven to 400°F and set the oven rack to the lower-middle position. Spray a 9×13-inch baking dish with nonstick cooking spray and set aside.
- Place the baguette slices on a metal rack placed inside a baking sheet and bake for 8-10 minutes or until golden brown. Remove from the oven and set aside until ready to use.16 oz. baguette
- While the bread slices toast, generously spray the inside of a large Dutch oven with nonstick cooking spray. Slice the onions (if they haven’t already been sliced).2 Vidalia onions, 3 yellow onions
- Add the butter, sliced onions, salt, black pepper, thyme leaves and bay leaf to the Dutch oven.¼ cup unsalted butter, 1 tsp kosher salt, ½ tsp freshly ground black pepper, 5 fresh thyme sprigs, 1 bay leaf
- Once the baguette slices have toasted, cover the Dutch oven tightly and cook the onions 1 hour. Remove pot from oven and stir, being sure to scrape the sides and bottom of pot.
- Return the pot to the oven with the lid slightly ajar and continue cooking another 1 hour.
- Once again, remove the pot from the oven and stir the onions (scraping the sides and bottom). The onions will be soft and a little darker than golden brown. If the onions need more color, return the pot to the oven (still with the lid slightly ajar) and cook another 30 minutes.
- Transfer the pot to the stovetop and turn the heat to medium-high. *Remember – the pot is HOT! Use oven mitts when touching the handles.*
- Remove and discard the bay leaf from the onions.
- Add sherry, beef broth and chicken broth; bring to a boil, stirring constantly, until slightly thickened, about 4-5 minutes.½ cup dry sherry, 1 cup unsalted beef broth, 2 cups unsalted chicken broth
- Layer half the toasted baguette slices in the prepared casserole dish.
- Spoon onion mixture evenly over the bread, and top the remaining bread slices.
- Sprinkle with shredded cheese and cover with foil.8 oz. freshly shredded Gruyere cheese
- Bake at 400°F for 30 minutes.
- Set the heat to broil and remove the foil.
- Broil 3 minutes or until cheese is bubbly. Watch closely.
- Garnish with additional thyme leaves, if desired.
Nutrition information is automatically calculated, so should only be used as an approximation.
Did you make this? Leave a comment!
How to Make French Onion Casserole Step by Step
Get the oven going and prepare a baking dish: Preheat the oven to 400°F and set the oven rack to the lower-middle position. Spray a 9×13-inch baking dish with nonstick cooking spray and set aside.
Bake the baguette: Bake the baguette slices in the oven at 400°F for 8-10 minutes and set aside.
Prepare the onions: Cut 2 Vidalia onions and 3 yellow onions.
Add ¼ cup unsalted butter, 1 tsp kosher salt, ½ tsp freshly ground black pepper, 5 fresh thyme sprigs, and 1 bay leaf into the prepared Dutch oven.
Cook the onions: Cook the onions in the oven at 400°F. After 1 hour, stir the onions and then place them back in the oven, with the lid slightly ajar. Cook another hour and stir again.
Transfer the pot of onions to the stove top and place over medium-high heat. Remove the bay leaf.
Add in the ½ cup dry sherry, 1 cup unsalted beef broth, and 2 cups unsalted chicken broth. Bring the mixture to a boil, stirring constantly, for about 4-5 minutes until it has thickened.
Make the casserole: Layer half of the baguette slices into the casserole dish. Then spoon the onions over each bread slice, and top with the remaining slices. Sprinkle the 8 oz. of cheese over everything.
Cover the casserole dish with foil, and bake for 30 minutes at 400°F.
After that, remove the foil, switch the oven to broil, and broil the casserole for about 3 minutes to make the cheese bubbly and golden brown.
Serve: Serve and enjoy!
How to Store
If you want to do some prep ahead of time, the baguette slices can be made up to 5 days ahead and kept in an airtight container until ready to use.
The caramelized onions can be made up to 3 days ahead and kept refrigerated, in an airtight container, until ready to use.
Store leftover French onion soup casserole in an airtight container in the refrigerator for up to 4 days.
Serving Suggestions
I like to serve this French onion soup casserole with a few light veggie-oriented sides, like a green goddess salad and either grilled veggies or air fryer roasted veggies to offset the rich cheesiness.
Darn Jenny you forgot to bit*h about the time to cut the onions, grade the cheese, slice the bread………
Hi Jenny, we apologize for the confusion. We are in the process of updating many of our older recipes. The timing for this recipe reflected active cook time, not the total passive cook time. It has been updated!
I am sorry to hear it didn’t quite work out!
I made this today exactly according to recipe (except I used mozzarella on top because I didn’t have gruyere). It was absolutely delicious! The concept of French onion soup as a casserole is perfect and had me thinking, “I wish I’d thought of that!” My husband and I both loved it and I will definitely make it again! I prefer it as a side rather than a main dish, but I want to try it again with vegetable broth as a main dish for my vegetarian family members. I think it will adapt nicely for my vege family! Loved it!!!
Thanks for stopping by and sharing, Cari!
Don’t know who timed this recipie but some one needs to add up the time.
Haha I thought the same thing, I was searching for a quick version of a French onion casserole and thought I found a winner but adding up the minutes its 198 minutes. How is 3.3 HOURS anywhere close to the mentioned 50 minutes total?!
Super disappointed, too. Googled French Onion Casserole recipes and chose this one since it said 10 min prep time, + 40 minute cook time. Went to the grocery store, got everything I needed only to come home and find out it’s actually close to a 3-hour ordeal. Timing needs to be updated, super frustrating because I prepared my dinner around this recipe and now have to order in!
This is a great recipe! If my family had their way, I would make it every day
Yay! Thanks, Chelsea!
This sounds wonderful to me. My husband is touchy about things getting too soft in recipes and I am wondering if the bread gets “squishy” in any way from soaking up juices, or does it retain a firmness. He is just so darn sensitive about these things. For example, I don’t leave the bread to soak whan making french toast. A quick dip, and immediately onto the hot skillet. Any feedback would be very much appreciated.
So the bottom layer of bread does get soggy and soaks up all that soup. I totally understand bc my husband is the same way. You could keep that layer out and just do the top layer (it stays pretty crisp). You could then serve in bowls like a soup, topped with a top piece of bread. Hope you enjoy!
Becky, thank you so much for the reply and the great suggestion! I will give that a try.
Let me know how it goes!
I added some deepfried crispy onion strings to add some more crunchiness :) not a bad touch. Definitely didn’t need it, though, this recipe rocked.
Hi, what can I substitute for sherry, please? Thanks.
Hi! You can use chicken stock or cooking sherry. Enjoy!
This looks so cheesy & delicious! I bet it’s a hit with everyone! Can’t wait to try it!
This recipe is insanely good!
I’m so glad you love it!