This french onion croissant bake is perfect for a super special breakfast or brunch. This gets prepared ahead of time and then is ready to bake before serving. It’s savory, cheesy and absolutely delicious!

Why is holiday brunch so fantastic?! 

overnight french onion croissant bake

This overnight french onion croissant bake is the epitome of holiday breakfast. It’s prepared ahead of time, completely indulgent, tastes wonderful, special, fancy and also feeds a crowd.

It checks all the boxes for a great holiday meal! 

caramelized onions

A few years ago I fell in love with this overnight croissant breakfast bake. We love it SO MUCH. I only make it once a year – sometimes twice. It is a very filling and decadent breakfast, and I have never made something that absolutely everyone loves so much.

We all look forward to this on holiday mornings. It’s unbelievably good. 

This year, I decided to “french onion” the breakfast casserole! Oh yes, I remove some of the spinach and instead, add a ton of caramelized onions. It tastes just as good as it sounds! 

caramelized onions

Here’s how I make it!

I start with the caramelized onions. This recipe is a little high maintenance because you have to caramelize the onions, then let this sit overnight. But I promise it is 100% worth it. 

I caramelize three or four large sweet onions. This will take around 60 to 90 minutes, maybe even longer. I like to start mine off a little higher, then turn them down after 20 minutes or so. I find that this really speeds up the process.

One reason I love this so much is because it’s made with croissants. I have always been a huge croissant lover! The base of this starts with croissants that are toasted until the broiler until they get wonderful, crisp and caramely bits. 

overnight french onion croissant bake

The custard is made with eggs, cream and freshly grated gruyere cheese. It melts like HEAVEN. 

Everything is tossed together: the toasted croissants, eggs, cheese and caramelized onions. Then it chills in the fridge overnight! This is key. You can’t skip this part!

In the morning, remove it from the fridge and bake it up. It’s cheesy, melty, crisp, crunchy, savory, sweet and everything you want. 

overnight french onion croissant bake

This gets so golden in the oven. The croissant pieces soak up all the egg and the mixture has the most perfect souffle-like texture.

overnight french onion croissant bake

I mean, just look at this!

overnight french onion croissant bake

This is a fabulous holiday brunch idea – or even one to make on christmas night after a day of lounging around. It’s incredibly satisfying.

And it’s feeds tons of people!

overnight french onion croissant bake

Plus, it’s one of the best things I’ve ever eaten!

overnight french onion croissant bake

French Onion Croissant Bake

Overnight French Onion Croissant Bake

This french onion croissant bake is perfect for a super special breakfast or brunch. This gets prepared ahead of time and then is ready to bake before serving. It's savory, cheesy and absolutely delicious!
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  • Heat the olive oil in a large oven-safe skillet over medium-heat. Stir in the onions with a big pinch of salt. Cook over medium, stirring often, until the onions soften, about 10 to 15 minutes.
  • Decrease the heat to low or medium-low. Cook the onions, stirring often, for about 60 to 90 minutes, until they are golden and caramelly. If at any time the onions start to burn, low the heat or add a few splashes of water to keep them hydrated.
  • Once the onions are golden and caramelly, transfer them to a plate. (Note: if you’re really in a rush, you can add 1 teaspoon of sugar, honey, maple syrup, etc to speed along the caramelization process. Be sure to stir often and check on the progress!)
  • While the onions are cooking, preheat the oven to 450 degrees F.
  • Place the croissants cut-side up on a baking sheet. Bake for 5 to 8 minutes, until the croissants are toasty. Remove and let them cool slightly, then chop or tear them into pieces.
  • Brush a 9x13 baking dish with melted butter. Place the croissants in the dish and toss them with half of the caramelized onions. Be sure to toss well so the onions are distributed evenly.
  • In a large bowl, whisk together the eggs, milk, heavy cream and a big pinch of salt and pepper. Stir in 1 cup of the gruyere cheese. I also like to stir in a handful of fresh chopped herbs, like parsley and thyme, but it’s up to you! Place the rest of the cheese in a bag stored in the fridge.
  • Pour the egg mixture over the top of the croissant mixture in the baking dish. Press any of the croissants into the egg liquid, making sure they are covered and absorbed the eggs. Top with the remaining caramelized onions.
  • Cover the dish with plastic wrap and refrigerate 8 hours, or overnight.
  • Preheat the oven to 350 degrees F. Remove the dish 30 minutes before baking to take the chill off.
  • Remove the plastic wrap. Top with remaining grated cheese stored in the fridge. Bake the dish uncovered for 45 to 60 minutes, or until the center is set. Top with some parmesan and a sprinkle of fresh thyme before serving. Serve!

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overnight french onion croissant bake

Happy holidaying!