The Best Vegetarian Breakfast Casserole

This Vegetarian Breakfast Casserole is the best way to start the day! Full of vegetables and protein, it’s hearty, cheesy, and full of savory flavor. Prepare it in advance for easy meals throughout the week.

close up image of a wooden spatula digging into a serving of vegetarian breakfast casserole.

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Some days it’s just good to have a break from meat in every meal, right?! This vegetarian breakfast casserole is perfect for anyone following a vegetarian diet, looking for ways to disguise healthy veggies from those picky eaters, or when you feel like a break from the usual bacon and sausage!

This meatless breakfast casserole can easily be adapted by swapping out the vegetables used in this recipe for those you love the most. It’s also a breeze to make ahead of time and simply pop in the oven when you’re ready to eat. Plus, the delicious smell from this breakfast casserole baking is enough to get the entire family around the table in no time!

Speaking of breakfast casseroles, be sure to check out my Cheesy Egg and Potato Breakfast Casserole, Amish Breakfast Casserole, Bisquick Breakfast Casserole With Bacon, and Eggs Benedict Casserole, too!

Vegetarian Breakfast Casserole Recipe

Vegetarian Breakfast Casserole is a complete meal with a healthy balance of protein, carbs, and fats. In addition, it’s full of fiber, minerals, and vitamins thanks to the assortment of vegetables. The combination of soft bread cubes, slightly crunchy veggies, puffy eggs, and melted cheese is simply irresistible.

Enjoy this Veggie Egg Bake casserole as is or alongside fresh fruit or a breakfast smoothie for a restaurant-worthy meal.

Ingredients for Vegetarian Breakfast Casserole

See recipe card below this post for ingredient quantities and full instructions.

Large eggs
Whole milk
Seasoning – Salt, ground black pepper, and cayenne pepper (optional).
Unseasoned stuffing bread cubes – Adjust the seasoning in this recipe if you use seasoned stuffing bread cubes instead.
Cheese – Shredded sharp cheddar cheese and gruyère cheese.
Butter – Salted or unsalted depending on your preference and dietary needs.
Vegetables – Diced onion, diced bell pepper (green and red), sliced mushrooms, halved cherry tomatoes, and frozen broccoli florets (thawed).

Variations

If you aren’t a fan of any of the veggies listed in this recipe, simply swap them out for those you do enjoy. This could include shredded zucchini, cubed potatoes, cauliflower florets, spinach, corn, cubed carrots, and peas. There are so many options!
Include bacon pieces, chopped ham, or ground sausage for a meaty version of this breakfast casserole.
Make this casserole dairy-free by using plant-based or dairy-free milk. Then, omit the cheese, or use dairy-free cheese.
Use gluten-free bread cubes for a gluten-free breakfast casserole.

large glass bowl with cubed bread soaked in a egg and milk mixture.

top down image of prepped vegetarian breakfast casserole ingredients sitting a large skillet.

How to Make Vegetarian Breakfast Casserole

Prepare: Preheat the oven, and grease a 9×13-inch baking pan with cooking spray. Set aside.
Make the egg mixture: Whisk the eggs in a bowl until smooth. Then, whisk in the milk and seasoning. Add the bread cubes, and stir to coat and moisten them. Allow this mixture to sit for 20 minutes while the bread soaks up the liquid.
Cook the veggies: While the bread soaks, add butter to a skillet. Once melted, cook the onions, mushrooms, and peppers on medium-high heat for 10 minutes, stirring occasionally. Stir in the broccoli, and cook for another 5 minutes to remove excess water. Remove the skillet from the heat and, mix in the tomatoes. Set the skillet aside.
Assemble the casserole: Stir the veggies and 1/2 cup of both types of cheese into the soaked bread mixture. Spread this mixture evenly into the prepared pan, and top it with the remaining shredded cheese.
Bake: Bake the casserole for 40 minutes. The top of the casserole should be golden and puffed up. Serve while hot!

serving of vegetarian breakfast casserole sitting on a stack of two plates.

Quick Tip

This vegetarian breakfast casserole can be assembled the night before and stored in the fridge, covered with foil or plastic wrap. Allow the uncooked casserole to sit at room temperature to warm up while the oven preheats. Then, bake as normal!

How to Store Vegetarian Breakfast Casserole

Store leftovers covered with plastic wrap or aluminum foil or in an airtight container in the fridge for up to three days. Or, freeze for up to three months. Thaw in the refrigerator overnight when you’re ready to serve.

Reheat your casserole in the oven at 350 degrees Fahrenheit until heated through. Or, warm individual portions in the microwave in 30-second increments until your desired temperature is reached.

Serving Suggestions

To keep this meal vegetarian, enjoy this comforting and hearty vegetarian breakfast casserole alongside these breakfast potatoes, a refreshing fruit salad, or a healthy green smoothie.

Otherwise, feel free to add some crispy oven-baked bacon and sausage balls to the breakfast table!

FAQs

What’s the difference between a frittata and a breakfast casserole?

A frittata features an egg mixture that cooks in a skillet on the stove before being transferred to the oven to bake completely.

A breakfast casserole consists of an egg mixture that is poured into a casserole dish and baked in the oven. There is no need for cooking on the stovetop!

Why is my breakfast casserole soggy?

If your casserole turns out soggy, it’s likely because too much liquid was used. You want to coat the bread pieces completely, but they shouldn’t be swimming in the egg mixture! In addition, be sure to allow the oven to preheat properly, and bake until the cheese is melty and the bread is lightly golden.

How do you know when a breakfast casserole is done?

The casserole will be golden brown on the top and will be puffed up. The liquid mixture should be set, and the casserole should feel slightly firm to the touch.