This French onion chicken casserole takes everything you love about a bowl of French onion soup and turns it into a hearty dinner you eat with a fork! Sweet caramelized onions and tender shredded chicken go under toasted baguette and melted Gruyere, all in one skillet. Start with a rotisserie chicken and it’s on the table in about 40 minutes!
More French Onion Favorites:
Before You Get Started
Most of what makes this casserole work happens well before the bread goes on top. Keep these three things in mind:
- Give the onions 20 minutes. Rushing this step leaves them sharp instead of sweet. Add a splash of water whenever the pan looks dry.
- Toast the bread first. Untoasted baguette soaks up the broth and turns to mush under the cheese.
- Use an oven-safe pan. The casserole finishes in the oven. A braiser or cast iron skillet works, or transfer everything to a baking dish.
Which Chicken to Use
You’ll need about 3 cups of cooked chicken, and just about any kind works.
- Rotisserie chicken: The shortcut I use most. One large bird gives you plenty. Just pull the meat and shred it.
- Boiled and pulled chicken: Simmer about 1 ½ pounds of boneless skinless chicken breasts or thighs for 15 to 20 minutes, then chop or shred.
- Leftover chicken: Grilled or baked chicken from an earlier meal works beautifully.
- Canned chicken: This works too. Drain it well first.
Picking the Right Cheese
Gruyère is what I call for, and it’s worth seeking out. If your store doesn’t carry it, a few other cheeses work well here.
- Most traditional: Comté, sometimes sold as Gruyère de Comté. Nutty and a little sweet, and it’s what you’d get in a French bistro.
- Best everyday swap: A block of regular Swiss. Closest to Gruyère in flavor and easy to find just about anywhere.
- Best for a melty top: Provolone, mozzarella, or Gouda. Milder in flavor, but they brown beautifully in the oven.
⇢ Grate the cheese yourself. Pre-shredded cheese is coated to keep it from clumping, and that coating keeps it from melting smoothly.
How to Make French Onion Chicken Casserole
This whole supper happens in one skillet with about 10 minutes of hands-on work. The onions take the longest, and everything after them moves quickly.
Step 1: Toast the Baguette Slices
Preheat the oven to 475°F. Arrange the bread slices on a baking sheet and toast them lightly, about 4 to 5 minutes. Set them aside.
They only need to be dry and lightly golden at this point. They’ll darken and crisp further later, so pulling them early keeps them from burning.
Try it another way
If you like making your own bread, my Baguette Bread Recipe is an easy homemade option.
Step 2: Caramelize the Onions
Melt the butter in an ovenproof skillet over medium-high heat. Add the sliced onions, season with salt and pepper, cover with a lid, and cook for 3 to 5 minutes until they soften.
Remove the lid, stir in the thyme and garlic, and keep cooking and stirring until the onions turn deep golden brown, about 15 minutes. As they cook, add a tablespoon of water and stir. Once it evaporates, add another. This keeps the onions and garlic from burning and it speeds up the caramelization at the same time.
You’re looking for onions that have collapsed down to a fraction of their original volume and turned the color of honey. If they’re browning faster than that, lower the heat to medium or medium-low.
Step 3: Build the Filling
Add the balsamic vinegar and Worcestershire sauce and cook for 1 more minute.
Then stir in the chicken and broth, scraping up any browned bits from the bottom of the pan. Those little bits add so much flavor to the casserole! Taste and season with salt and pepper.
Bring the mixture to a boil, then pull the pan off the heat.
⇢ Chicken broth or beef broth both work. Beef gives you a deeper, more traditional French onion flavor. Chicken keeps it lighter. Use low sodium either way if you’re watching the salt.
⇢ Skip the chicken for a meatless version. Two cans of drained, rinsed white beans stand in nicely. If you’d rather have it over pasta, my French Onion Pasta Bake with Spinach and Mushrooms is built on the same flavors.
Step 4: Add the Bread and Cheese
Arrange the toasted bread slices over the chicken and onion mixture in a single layer, then sprinkle the cheese evenly over the top.
Step 5: Bake Until Golden
Slide the skillet back into the 475°F oven for 5-10 minutes, until the cheese melts and starts to brown in spots.
Keep a close eye on the pan the entire time, because the cheese and bread can go from golden to burnt quickly.
Garnish with chopped fresh parsley or thyme if you’d like, and serve right away while the top is still crisp.
⇢ Prefer a darker browned topping? Broil the casserole for a few minutes instead of baking it. Just keep a close eye on it since the bread and cheese can burn quickly under the broiler.
What to Serve Alongside
This is a rich, cheesy dinner with the bread already built in, so something fresh and simple next to it is all you need. My House Salad with Candied Pecans is what I’d put on the table first, since the sweetness in the pecans and cranberries pairs well with the caramelized onions.
A simple green vegetable works just as well, and most of these roast in about the time it takes the onions to cook down. Here are some we love:
Storage, Freezing, and Reheating
To store: leftovers keep in an airtight container in the refrigerator for 3 to 4 days. The bread softens as it sits, so this one is definitely best the night you make it.
To freeze: freeze the chicken and onion filling on its own, without the bread and cheese, for up to 3 months. Thaw overnight in the fridge, warm it gently on the stovetop, then add fresh toasted bread and cheese and bake. That’s the version worth making ahead for someone else’s freezer, since you skip the soggy bread entirely.
To make ahead: the chicken and onion mixture can be made up to a day or two in advance. Cover and refrigerate, then warm it through on the stovetop before topping and baking.
To reheat: cover loosely with foil and bake at 350°F for 15 to 20 minutes, until warmed through. Individual portions reheat in the microwave in 1 to 2 minutes.
Frequently Asked Questions
Can I use raw chicken instead of cooked?
This recipe is built around cooked chicken, so raw chicken won’t work as a straight swap. The filling only simmers for a minute before it goes in the oven, which isn’t nearly enough time to cook chicken through.
If raw is what you have, cut it into bite-sized pieces and sauté it in the skillet until cooked through before you start the onions, then set it aside and stir it back in at the broth stage.
Can I make this in a baking dish instead of a skillet?
Yes, and it’s an easy swap. Cook the onions and filling on the stovetop as written, then transfer everything to a 2-quart baking dish or an 8-inch or 9-inch square dish before you add the bread and cheese. Bake it the same way.
Why aren’t my onions turning golden brown?
Usually it’s heat or crowding. If the pan is packed too tightly, the onions steam instead of browning, so use a wide skillet and give them room. If they’re just sitting there pale after 15 minutes, nudge the heat up a little and stir more often. And don’t leave the lid on past the first few minutes, since trapped steam keeps them from caramelizing at all.
Can I use canned French onion soup or onion soup mix instead?
You can, and it’s a reasonable shortcut on a busy night. Swap the broth for a can of condensed French onion soup, or stir a packet of onion soup mix into a cup of broth. You’ll lose the deep sweetness that comes from cooking real onions down slowly, and the dish gets saltier, so hold off on adding salt until you taste it. If you go this route, sauté a sliced onion for a few minutes first to get at least some of that flavor back.
How do I keep the bread from getting soggy?
Toast it well, slice it about a half inch thick, and serve the casserole soon after it comes out. Thin slices soak through almost immediately, and untoasted bread has nothing to hold it together once it hits the broth. If you know you’ll have leftovers, you can also spoon the filling into the dish, portion out what you’re serving, and add fresh toasted bread and cheese to each round.
More Cozy Chicken Casseroles
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Watch How to Make It
French Onion Chicken Casserole
Equipment
Ingredients
- 2 tablespoons salted butter
- 1 lb. Vidalia onions, or other sweet onions, thinly sliced (about 2 medium onions)
- Kosher salt and ground black pepper, to taste
- 1 teaspoon minced fresh thyme leaves (or about ¼ teaspoon dried thyme)
- 1 clove garlic, peeled and minced or pressed
- 1 tablespoon balsamic vinegar
- 1 teaspoon Worcestershire sauce
- 3 cups cooked, diced or shredded chicken (such as the meat from a rotisserie chicken)
- 1 cup chicken stock or beef broth
- 9 to 10 slices crusty French baguette (or other similar bread), sliced about ½-inch thick
- 1 cup grated Gruyere cheese (or sub with grated Swiss cheese)
- Optional, for serving: chopped fresh thyme or parsley for garnish
Instructions
- Toast the bread: Preheat oven to 475°F. Arrange the bread slices on a baking sheet and toast lightly, about 4 to 5 minutes. Set aside.
- Soften the onions: Melt the butter in a medium ovenproof skillet over medium-high heat. Add the onions and season with salt and pepper. Cover with a lid and cook, stirring occasionally, until softened, about 3 to 5 minutes.
- Caramelize: Remove the lid, stir in the thyme and garlic, and continue cooking and stirring until the onions are deep golden brown, about 15 minutes. As they cook, add a tablespoon of water and stir. Once it evaporates, repeat with additional tablespoons of water. This keeps the onions from burning and speeds up caramelization.
- Add the vinegar: Stir in the balsamic vinegar and Worcestershire sauce and cook for 1 more minute.
- Add chicken and broth: Stir in the chicken and broth, scraping up any browned bits from the bottom of the pan. Taste and season with salt and pepper. Bring to a boil, then remove from the heat.
- Top it: Arrange the toasted bread slices over the chicken and onion mixture in a single layer, then sprinkle the cheese over the top.
- Bake: Place the skillet in the 475°F oven for 5-10 minutes, until the cheese melts and starts to brown.
- Serve: Garnish with chopped fresh parsley or thyme, if desired, and serve right away.
Notes
- Pan: I use this 2.25-quart Le Creuset braiser, an oven-safe skillet with a lid. A 9-inch or 10-inch cast iron skillet also works well. No oven-safe skillet? Transfer the filling to a 2-quart baking dish before topping.
- Chicken: Use rotisserie, boiled and pulled, leftover, or canned chicken. You’ll need about 3 cups.
- Cheese: Comté is the most traditional choice, Gruyère is the easy stand-in, and Swiss, provolone, mozzarella, or Gouda all melt well. Grate it yourself rather than buying pre-shredded.
- Broth: Beef broth gives a deeper, more traditional flavor and chicken broth keeps it lighter. Both work.
- Storage: Leftovers keep in an airtight container in the refrigerator for 3 to 4 days. The bread softens as it sits, so this is best the day it’s made.
- Freezing: Freeze the chicken and onion filling on its own for up to 3 months, without the bread and cheese. Thaw, warm on the stovetop, then top with fresh bread and cheese and bake.
- Reheating: Cover loosely with foil and bake at 350°F for 15 to 20 minutes, or microwave individual portions for 1 to 2 minutes.
Nutrition
Originally published in December, 2022, this post was updated in October, 2026.
Hey Sarah. I’m trying to fill my parents freezer with some meals they can take out if the freezer and bake. Do you think there’s a way to do that with this recipe? Thanks!
Hi Julie,
This recipe can be frozen for up to 3 months, but the bread will get soggy as the dish sits. So, it’s best eaten right away.
If I wanted to prep the chicken and onions the night before and then assemble and bake from cold the day of, how would you recommend altering the baking instructions?
Hi, Sarah! You can fully cook the onions and prepare the chicken and broth filling the night before. Transfer to a baking dish, cover, and refrigerate, keeping the bread and cheese separate.
The next day, let the dish sit out while the oven preheats to 350°F. Cover with foil and bake for about 25 to 35 minutes, or until the filling is hot throughout. Remove the foil, increase the oven temperature to 475°F, and add the toasted bread and cheese. Bake uncovered for another 5 to 10 minutes, until the cheese is melted and lightly browned. This gives the cold filling time to heat through before the topping gets too dark!