web analytics

Easy Vegetarian Make-Ahead Breakfast Casserole

This wonderfully savory make-ahead breakfast casserole is brimming with vegetables. It’s perfect to feed a crowd on Christmas morning or at a festive brunch.

Easy Vegetarian Make Ahead Breakfast Casserole | Umami Girl

I won’t bury the lede. We’ve become obsessed with this casserole. It all started with some leftover stuffing cubes from Thanksgiving. The really good kind where Whole Foods dries out all their little bits of leftover bakery bread, from sourdough to pumpernickel, and hands it to you in a bag that lasts approximately forever (like definitely until — not asking questions).

We’re not inherently a casserole family. I feel about 40 years too young and altogether not midwestern enough to aspire to something like that. It’s not that we don’t like family-style dishes baked lovingly in the oven and served alongside a simple green salad. We TOTALLY like that kind of food. Speaking for myself, I probably like it a little too much from time to time. But when I hear the word “casserole,” I think of someone else. I don’t know — deep food thoughts for the day. 

Easy Vegetarian Make Ahead Breakfast Casserole | Umami GirlAnd yet. Here we are with this happy-making CASSEROLE. (I might call it Breakfast Strata in private, okay?) It’s brimming with vegetables — onion, shiitakes, Christmas-colored peppers and broccoli. It’s super-savory. It’s pretty good for ya, considering. And it tastes SO good.

Easy Vegetarian Make Ahead Breakfast Casserole | Umami GirlI can think of two scenarios where this dish would be the answer to your wildest dreams. (No presh, Umami Girl.) First: Christmas morning, or any morning when you have sleepover guests and don’t feel like cooking breakfast to order. You can make this dish a whole day in advance and take it out of the fridge when you wake up in the morning. It bakes in 40 minutes, during which time you’re free to be doing absolutely whatever else you like.

Easy Vegetarian Make Ahead Breakfast Casserole | Umami GirlSecond: this would be a fabulous anchor point for a festive and casual brunch, any time of year but especially around the holidays. Here’s what I would do:

The Perfect Casual Holiday Brunch

At this time of year, and especially this year, I love the idea of creating an event where guests feel cozy and totally low-key, where everyone can spend time together just feeling merry and without a lot of expectations. All you need is:

Food: Something savory and something sweet. If you’re making this casserole, how about serving it with a simple green salad, a big bowl of fruit salad, and some muffins or Lotta Jansdotter’s cinnamon rolls. don’t be shy about asking guests to bring something.

Drinks: Good coffee and one signature cocktail. For brunch I always gravitate toward seasonal champagne cocktails (these can be as simple as adding a splash of pomegranate juice to a glass of bubbly) or my favorite Bloody Mary recipe.

Music: My favorite trick is to ask the occasional guest to make me a new Pandora station. It’s a great way to expand your listening repertoire.

Invitations:  Paperless Post has some great online holiday party invitations this year that look pretty and classy without creating a lot of work or environmental burden. (And while you’re at it, I like their holiday card line as well, especially the ones marked (RED), where they donate 25% of proceeds to help fight AIDS.)

Activity: Totally optional, but I LOVE the idea of putting out a little coloring station so kids can send holiday cards to our troops through the Red Cross Holidays for Heroes program.

Easy Vegetarian Make Ahead Breakfast Casserole | Umami Girl

That’s it! NBD. Have fun. Talk to you soon.

Carolyn xx

P.S. Affiliate links follow.

Easy Vegetarian Make-Ahead Breakfast Casserole

Preparation 30 min Cook Time 40 min Total Time 1:10
Serves 10     adjust servings

I like to use my 5-quart braiser for this dish, because it can go from stovetop to oven. If you don’t have one of those, you can do the stovetop part in a 12-inch skillet and the baking part in any 5-quart baking dish. You can prepare this casserole the day before, store it tightly covered in the fridge and bake it the next morning. Remove from fridge about an hour before baking if possible, otherwise it may need to bake a little longer.


  • 4 tablespoons butter
  • 1 medium yellow onion, diced
  • 1 green bell pepper, diced
  • 1 red bell pepper, diced
  • 10 ounces sliced shiitakes
  • 1 teaspoon salt, divided
  • 10 ounces frozen chopped broccoli, defrosted
  • 10 large eggs
  • 3 cups whole milk
  • 1/8 teaspoon nutmeg
  • Pinch ground cayenne
  • Freshly ground black pepper
  • 8 cups unseasoned dry stuffing cubes/bread cubes
  • 5 ounces shredded gruyere, divided
  • 4 tablespoons grated parmesan or pecorino, divided


Melt the butter in the braiser or skillet over medium-high heat. Add the onion, peppers, and shiitakes all at once, along with 1/2 teaspoon of the salt. Cook, stirring from time to time, for about 10 minutes, until the vegetables have softened, browned a bit, and decreased in volume by at least half. Remove from heat.

While the other vegetables cook, place the defrosted broccoli on a thick layer of paper towels and cover with another thick layer. When the veggies in the skillet have cooked as noted above, press down gently on the paper towels to remove moisture from the broccoli. The add broccoli to the skillet and stir to incorporate.

Crack the eggs into a large mixing bowl and beat well with a fork. Stir in milk, nutmeg, cayenne, and a few good grinds black pepper. Add bread cubes and stir to moisten. Then stir in all the vegetables, half the gruyere and half the parmesan or pecorino. Pour the whole mixture back into the braiser or into the baking pan and sprinkle with the remaining cheese. Cover and refrigerate overnight or for at least a few hours before proceeding. Remove from fridge about an hour before baking if possible.

An hour before serving time, preheat oven to 375°F with a rack in the center. Bake uncovered for about 40 minutes, until puffed and golden. Serve hot or even at room temperature.


Recipe Notes

2 reviews
This savory make-ahead vegetarian breakfast casserole is perfect for Christmas morning or your next brunch.


Hi there, I'm Carolyn, and I'm delighted you're here. I'm a NYC-area food, travel, yoga, coffee, wine, running, music making and book obsessive with a great family and a love for sharing it all with you. Grab a drink and come on in. Learn more.

Error: Access Token is not valid or has expired. Feed will not update.
This error message is only visible to WordPress admins

There's an issue with the Instagram Access Token that you are using. Please obtain a new Access Token on the plugin's Settings page.
If you continue to have an issue with your Access Token then please see this FAQ for more information.