Overnight Breakfast Casserole

This easy make ahead breakfast casserole is simple, healthy and delicious! It can be made the night before and left to sit overnight for the perfect balanced breakfast or brunch the next day! A family favourite that is great for meal prep or serving company during the holidays or anytime of year!

Overnight Breakfast Casserole

When you have a hungry tribe to feed in the morning, this breakfast egg casserole is an easy and effortless option. Made with just a few simple ingredients, it can be made the night before and baked in the oven in the morning for a delicious feast perfect for a crowd. It also works well for weekly meal prep for those crazy busy mornings!

Made with lean sausage, eggs and bell peppers it’s a great option for breakfast or brunch and it takes minimal time to prepare. Packed full of protein and fibre, it’s the perfect satisfying morning breakfast that the whole family will love!

For more make ahead breakfasts, be sure to check out my Egg White Breakfast Casserole, Blueberry French Toast Casserole, and Freezer-Friendly Breakfast Burritos.

Why Make this Recipe

• With the eggs, sausage, cheese and milk, this easy breakfast casserole is also a great source of protein which can leave you feeling full and satisfied, so you’re less likely to arrive at the dinner table feeling ravenous and wanting to eat everything in sight.
• The whole-grain bread and veggies also offer a nice kick of fibre to help keep that digestive system in gear.

Ingredient Notes

Eggs: The eggs form the base of the recipe and add lots of high-quality protein. Use brown or white; there is no nutritional difference.

Sausages: Use lean breakfast sausages or turkey sausages to reduce saturated fat content. If vegetarian, you can also use a meat-free or plant-based sausage, or leave the sausage out all together. You can also use ground sausage or remove the sausage from the casing if you prefer the sausage to be more evenly distributed throughout the casserole.

Bread: You can use whole grain bread or sub in gluten-free if there are any intolerances. French bread or sourdough bread also work well.

Milk: We use regular 1% milk when making this casserole, but you can sub in your preferred milk or milk alternative to make it dairy-free.

Peppers: Are a great way to add some nutrient-rich vegetables into this dish. I used red and green to add a nice pop of colour and to make it more festive, but feel free to use other colours. You can also sub in other vegetables like spinach, kale, asparagus or broccoli, if desired.

Cheese: I used an old cheddar cheese for extra flavour. Feel free to use your preferred cheese or sub in a plant-based cheese to make it dairy-free. Other cheeses that would work well include Swiss, pepper jack cheese, gouda or mozzarella.

Step by Step Instructions

• In a frying pan over medium heat, brown sausages, about 6-7 minutes. Remove the sausages from the pan and pat down well with paper towel to get rid of excess grease.

• In the same pan, cook the peppers for about 5-6 minutes or until softened.

• In a medium-sized bowl, beat eggs with milk, salt, pepper and dry mustard.

• Spray a 9 x13 inch casserole dish with cooking spray or grease using your preferred method.
• Distribute sausages evenly across the bottom of the dish. Next, evenly spread the cubed bread and sliced peppers on top of the sausages. Pour the egg mixture over the sausage, bread and peppers. Top with shredded cheese.

• Allow casserole mixture to sit in the fridge for at least 2 hours or overnight.
• When ready to bake, preheat oven to 350 degrees F. Bake for 60-80 minutes or until egg is set when you cut into it and casserole is slightly browned and puffy on the top. Allow the casserole to cool for at least 15 minutes to allow it to set.

Recipe Tips:

• Use lean sausages to eliminate excess saturated fat. An increasing number of grocery stores are starting to offer this now. Or you could even sub in turkey breakfast sausages as well.
• Be sure to pat down the sausages well with paper towel after cooking to eliminate any excess grease.
• To make this vegetarian, leave out the sausage and add an extra cup or so of vegetables.
• You may wish to toast the bread or use bread that is a couple of days old so that it has a chance to dry out. This will make the bread a little more crusty and will help it better absorb the egg mixture.
• If you choose to add more vegetables, make sure that you cook them first to allow some of the moisture to evaporate from them before adding them to the baking dish to prevent the casserole from becoming soggy.
• The egg casserole is done when the egg is no longer runny and it’s puffy and golden on top.
• Allow the casserole to sit for at least 15 minutes to allow it to set before cutting.

Recipe FAQs

Does the breakfast egg casserole have to sit overnight?

Not necessarily. Although it’s called an overnight breakfast casserole, if pressed for time, you don’t have to let it sit overnight. I would say that letting it sit for at least 2 hours before putting it in the oven would be sufficient. That’s what I did last time I made it and it turned out just as good as when I let it sit overnight.

Can I add more veggies?

Of course! This is a really versatile recipe and you can easily add in whatever vegetables you have on hand. Other vegetables that would work well include mushrooms, spinach, kale, asparagus or broccoli.

Just be sure to cook them first if they tend to be more watery to allow some of that extra moisture to evaporate before combining with the rest of the casserole ingredients.

What type of bread should I use?

This make ahead breakfast casserole can be made with most types of bread. I used 100% whole-grain bread, but you can use gluten-free and sourdough and French bread also work really well. It’s best if you bread is a day or two old as it will be dryer and will soak up all of the flavours from the egg mixture.

How long does it keep?

If you have leftovers, you can store them covered in the fridge for up to four days.

How to reheat egg casserole without overcooking?

The key to preventing the casserole from overcooking when reheating is to cover the baking dish with foil. This ensures that the moisture will not escape and helps promote even heating. To reheat, cool to room temperature and place the casserole in the oven preheated to 350F for 20-30 minutes or until heated through.

Do egg casseroles freeze well?

Yes, the beauty of this recipe is that you can freeze it for later. To do so, prepare the recipe through step 5, then cover the casserole with plastic wrap, then a piece of aluminum foil. Freeze for up to 3 months.

When ready to cook, allow to thaw overnight in the refrigerator. Bring to room temperature, then continue with step 6.

Serving Suggestions

Although this casserole is pretty filling on its own, you could always serve it along with some muffins (these Flourless Apple Muffins are delicious!), and a nice fruit salad if you’re serving it for breakfast (try this Christmas Fruit Salad or Christmas Fruit Wreath).

It also pairs well with roasted sweet potatoes or this Spinach Orange Salad or Christmas Wreath Salad if serving it as more of a lunch or dinner option. Either way, you can’t go wrong!

More similar recipes

• Crustless Asparagus Quiche
• Low Carb Quiche 
• Scrambled Eggs without Milk
• Sheet Pan Sausage and Veggies
• Turkey Sausage Egg Muffins
• Spinach Zucchini Frittata Fingers

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This recipe was originally posted in December 2018 and was updated in December 2020 to include more helpful tips and photos.

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