Fluffy, savory, and cheesy egg squares belong on every holiday plate! This Vegetarian Overnight Breakfast Strata is an amazing breakfast casserole for special occasions. Not only is it absolutely delicious, it’s a make-ahead breakfast bake that you assemble the night before, so that the morning of the big day, all you need to do is bake it. Easy!

I make this breakfast strata every Christmas! It’s a great way to get a dose of protein in alongside pastries, muffins, and other inevitable holiday breakfast treats. And it makes holiday mornings special!

Table of Contents

The Story Behind the Recipe

Like many recipe stories, this one begins with my Mom. She made a version of breakfast strata every Christmas morning. It was delicious and satisfying and made enough for leftovers.

Ahhhh … the leftovers. A square of warmed up breakfast strata and some of my Gran’s leftover dinner rolls sliced up, toasted, and buttered … we’re talking the good life right there.

My mom’s version of this overnight breakfast casserole involved cream of mushroom soup and chopped up sausage links. I’m not sure where the soup came in, and I’m now a vegetarian, so no sausage for me.

This version, Vegetarian Overnight Breakfast Strata, is the one I now make for my family every Christmas. Oftentimes, I’ll make two of them, adding browned crumbled sausage to the second one for my guy and any other meat-eaters at the table.

Why You’ll Love This Vegetarian Overnight Breakfast Strata

There is just something so deeply satisfying about making a hearty, delicious breakfast with literally no effort on the morning of a special occasion. This vegetarian breakfast casserole is a bit of work to assemble the night before, but it is SO worth it!

Plus, it tastes so good. The eggs and cheese transform into kind of a soufflé consistency. The veggies add some interest, but the cheesy bits are the best, in my book.

Ingredients

  • Eggs – Lots of em! I use large eggs.
  • Milk – Whole milk works well, or half and half for a richer egg strata. I’ve also often used unsweetened oat milk or almond milk to reduce the dairy, and it works great!
  • Bread – Plain old white bread, please, with the crusts trimmed.
  • Cheese – I like to use a medium cheddar. Sharp cheddar, white cheddar, or gruyere are fantastic in this vegetarian breakfast casserole as well.
  • Olive oil – For sautéing the veggies.
  • Onion – Diced, for a bit of texture and flavor.
  • Green pepper – I love the color and flavor green bell pepper adds to egg strata.
  • Mushrooms – These are optional (I know mushrooms can be polarizing!) But I love them. White button mushrooms or cremini mushrooms both work.
  • Salt & pepper – always!
  • Parsley – optional, but pretty when sprinkled over the top of your strata.

Adaptations/Variations

Add meat or make it a one-dish-two-ways recipe: Sometimes I’ll make one big meatless version in an 8″ x 8″  pan, then just cook up some bacon to serve alongside for the meat-eaters. Other times, like this one, I split the strata into two smaller casserole dishes and add sausage to the meat side. I adore Morningstar Farms’ Veggie Sausage Patties, so this time I cooked up a couple of those and added them to my veggie version as well. It was great.

Make it dairy-free: I’ve made this with dairy-free milk and I’ve both omitted the cheese, and subbed in vegan cheese. Both work well.

How to Make This Vegetarian Breakfast Casserole

First, you sauté the veggies. In a large bowl, whip together the eggs, then stir in the milk, salt, and pepper.

Layer half your bread in your baking dish, then top with the cooked veggies and cheese then pour half the egg mixture over the top. Repeat the layers.

Cover tightly and store in the fridge overnight.

About an hour before breakfast, bake your egg strata until it’s set all of the way through. The middle should no longer jiggle. It will take almost an hour to bake, but it’s all hands-off time. This is when we dig into our Christmas stockings and see what’s under the tree!

Tips for Success

  • Use the most basic white bread possible. We’re talking white sandwich bread.
  • Make sure it’s set all the way through. Sometimes it takes awhile to cook in the middle, but it will – just give it time! It shouldn’t jiggle in the middle when it’s done.

More Strata Recipes

Holiday Breakfast Strata with Sausage (or Not)
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Holiday Breakfast Strata with Sausage (or Not)

Prep: 25 minutes
Cook: 45 minutes
Total: 1 hour 10 minutes
Author: Kare
Yield: 12
This easy overnight breakfast strata is cheesy, delicious, and perfect for holiday mornings! When time is tight and a special breakfast is in order, this fits the bill on both counts.

Ingredients

  • 1 tablespoon olive oil
  • 1 cup chopped onion (about 1 small onion)
  • 1 cup chopped green bell pepper (about 1 medium green bell pepper)
  • 1 cup white button mushrooms (sliced)
  • 9 eggs
  • 3 cups whole milk (unsweetened oat milk also works)
  • 3/4 teaspoon kosher salt
  • 1/4 teaspoon freshly ground black pepper
  • 12 slices white bread (crusts removed)
  • 10 ounces medium cheddar cheese, shredded (about 2 1/2 cups)
  • parsley (minced, for garnish)

Instructions

  • In a medium saute pan, heat the olive oil and saute the onion, green pepper, and mushrooms until soft, about 7-8 minutes. Set aside.
  • In a medium bowl, whisk the eggs until well blended. Add the milk, salt, and pepper.
  • Spray a 9"x13" casserole dish with non-stick cooking spray.
  • Layer half the bread in the bottom of the baking dish. Sprinkle 1/2 of the veggies over the top, then half the cheese. Pour 1/2 cup of the egg mixture over the top. Repeat with the remaining ingredients – first the bread, the rest of the veggies, the cheese, then the eggs. Press any bread down gently that's floating so that it becomes submerged.
  • Cover tightly and refrigerate overnight, or for at least three hours.
  • In the morning, uncover and bake at 350 degrees Fahrenheit for about 50 minutes, until set and no longer jiggly in the middle.
  • Garnish with parsley, cut into squares, and serve.

Notes

Recipe update 4/3/2024:
I’ve rewritten this recipe to simplify it, making one large vegetarian strata instead of two smaller stratas. If you like, you can easily divide this recipe between two smaller pans, adding cooked sausage to one, and baking so that you have two versions, one for the meat-eaters and one for the vegetarians. 

Old recipe:

Ingredients
  • 1 tablespoon olive oil
  • 1/2 cup chopped onion
  • 1/2 cup chopped green pepper
  • 3/4 cup white button mushrooms
  • 6 eggs
  • 2 cups half and half
  • 1/2 teaspoon salt
  • Fresh ground pepper
  • 8 slices white bread (crusts removed)
  • 2 cups cheddar cheese, shredded
For the meat half, if making:
  • 1/2 pound sausage
Instructions
  • In a medium saute pan, heat the olive oil and saute the onion, green pepper, and mushrooms until soft, about 7-8 minutes. Set aside.
  • If using sausage, brown it in a medium saute pan and drain.
  • If using veggie sausage, heat it in the microwave for a minute or so and crumble.
  • In a medium bowl, whisk the eggs, half and half, salt, and pepper.
  • Spray two approximately 4″ x 8” baking pans/casserole dishes with non-stick cooking spray.
  • Layer two slices of the bread in the bottom of each pan.
  • Sprinkle 1/4 of the veggies over the bread in each pan.
  • Spread half the crumbled sausage over the sausage version.
  • Sprinkle on 1/4 of the cheese over each.
  • Pour about 1/2 cup of the egg mixture over the top.
  • Add a layer of the remaining bread, two more slices each, then veggies, then sausage over the sausage side, then cheese.
  • Pour the rest of the egg mixture evenly over the top of each.
  • Cover tightly and refrigerate overnight, or for at least three hours.
  • In the morning, uncover and bake at 325 degrees for about 40 – 50 minutes, until set.

Nutrition Facts

Serving: 1square, Calories: 268kcal, Carbohydrates: 18g, Protein: 15g, Fat: 15g, Saturated Fat: 7g, Polyunsaturated Fat: 2g, Monounsaturated Fat: 4g, Trans Fat: 0.02g, Cholesterol: 154mg, Sodium: 490mg, Potassium: 252mg, Fiber: 1g, Sugar: 5g, Vitamin A: 560IU, Vitamin C: 11mg, Calcium: 318mg, Iron: 2mg
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