This flexible, high-protein breakfast casserole is the kind of "anything goes" recipe you’ll want to keep in rotation. Easy to prep, great for using up leftovers and perfect for your busy mornings.
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Breakfast at a Glance
- Prep Time: 10-15 minutes hands on; 1 hour total
- Planning Ahead: Meal prep it ahead of time for or make it when you plan to eat it (if you aren't short on time)
- Morning Effort: Just reheat (you can use the microwave) and eat
- Protein: ~19+ grams per serving, depending on your add-ins
- Fiber: Depends on your mix-ins and sides
Nessy's Note
Meet the recipe I’ve probably made more than any other.
Some version of this casserole (such as sweet potato egg bake) ends up in our fridge nearly every week- packed with whatever veggies, meat or cheese we have on hand.
It’s endlessly adaptable, surprisingly delicious and a great way to make sure nothing in the fridge goes to waste. Plus having it in the fridge is an absolute life saver on busy mornings!
Ingredients and Substitutions
The exact amounts can be found in the recipe card, but let's just talk quickly about the key ingredients and substitution options:
- Eggs- The base of the casserole and main source of protein. No substitute here!
- Greek Yogurt- Gives the casserole a smooth, creamy texture (no one wants rubbery eggs) and provides extra protein (it does the same for Greek yogurt scrambled eggs).
- Substitution: You can substitute with skyr. I don't recommend using regular yogurt as it is a bit too thin and the casserole may not set properly. But if you'd like to use cottage cheese, check out this Cottage Cheese Breakfast Casserole instead!
- Sea Salt + Black Pepper- A little basic seasoning goes a long way for this simple breakfast casserole.
- Substitution: Table or kosher salt can also be used- adjust to taste as needed. Depending on your mix ins, you can experiment with other seasonings as well such as garlic powder or Italian herbs.
- Add-ins- Almost anything goes with this casserole. Use what you have on hand- leftover vegetables (I love using up roasted veggies that we have leftover from the week), greens, cheese, cooked sausage or bacon, beans, herbs or dried out bread (cut it into cubes). I make this casserole almost every weekend and it always looks a little different depending on what we have in the fridge to use up!
Meal Prep, Make Ahead + Storage Tips
This high protein breakfast casserole is a dream for breakfast meal prep (Did I mention make it almost every week?)!
- Make-Ahead: While I don't recommend prepping the full casserole ahead of time and leaving it unbaked in the fridge (the eggs can separate), you can prep your mix-ins in advance. Cook and chop your veggies or meats, store them in the fridge and finish assembling when you are ready to bake.
- Meal Prep for the Week: After baking and resting, slice it into portions and store in airtight containers in the fridge for up to 4 days. You can store multiple squares in the same container if you like.
- To Freeze: This casserole freezes beautifully. Let it cool fully in the fridge with covered loosely to limit moisture buildup. Once cold, portion into containers and freeze for up to 3 months.
- Reheating: Thanks to the yogurt, this reheats well in the microwave without tasting too "egg-y". Heat until warmed through. You can also use the oven: preheat to 350°F and bake the casserole or portion that you're reheating for 15-20 minutes or until heated through.
Troubleshooting
- Too watery? This can happen if you use a lot of veggies that had too much moisture (especially mushrooms, spinach or zucchini) or if they weren’t cooked before baking. If you are using a large amount of them, sauté or roast water-heavy vegetables first.
- Didn’t set properly? It likely needed more baking time, or your oven temp was too high- causing the outside to brown before the center was fully cooked. Make sure to bake until the center is fully set (a gentle wiggle is okay, but it shouldn’t be "sloshy").
- Stuck to the dish? Use a glass casserole dish- I personally find it sticks less than metal. You can also try greasing your dish very well or line the bottom with a silicone mat if needed for easy removal.
Make it Your Own
This casserole can easily to customized to what you have or you can adjust it depending on what sorts of nutrients you want to include! I have personally added all of the following at one point or another when making this casserole:
To add fiber and carbs, try:
- Vegetables such as spinach, kale, mushrooms, bell peppers, broccoli, zucchini, onions or tomatoes
- Roasted potatoes or sweet potatoes
- Cooked beans or lentils (might sound strange but they are surprisingly good)
- Cubed or torn sourdough bread
To increase protein, you can add:
- Shredded or crumbled cheese such as cheddar, mozzarella, goat cheese or feta
- Cooked sausage, bacon or ham
- Beans or lentils
And to change up or add some more flavor, you can include:
- Spices such as smoked paprika, cumin, garlic powder, chili flakes or Italian seasoning
- Roasted garlic or chopped sun-dried tomatoes
- Fresh herbs like parsley, chives, basil or dill
- Sauces such as chimichurri, pesto or hot sauce (but don't add more than 2-3 tablespoons of liquid or the casserole may not set properly)
My Top Tips for the Best High Protein Breakfast Casserole
- Add some sides to balance it out. Pair with roasted potatoes, fruit or any of these sides I suggest for scrambled eggs would also be delicious for rounding out your breakfast with fiber or whatever else you might need.
- Don't be afraid to experiment. This casserole is perfect for using up odds and ends- think leftover roasted veggies, end of the week produce, cheese or meat.
- Bake at 350°F. After literally dozens (if not hundreds) of test batches, I have found that this is the optimal temperature to ensure it cooks through in the center without burning on the outside.
More Make Ahead Breakfast Recipes...
If you give this recipe a try, be sure to let me know what you thought in the comments below!
High Protein Breakfast Casserole
This flexible, high-protein breakfast casserole is the kind of "anything goes" recipe you’ll want to keep in rotation. Easy to prep, great for using up leftovers and perfect for your busy mornings.
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Servings
Equipment
- 7x11 or 9x9 inch casserole dish (at least 2 inches deep)
Ingredients
- 12 large eggs
- 1 and ½ cups Greek yogurt
- ½ teaspoon fine sea salt
- ½ teaspoon black pepper
- 2-3 cups add-ins
Instructions
- Cook any meat or hard vegetables (like potatoes) before assembling. You can cook them separately or roast them directly in your casserole dish to save an extra pan. Chop your veggies, shred your cheese, etc.Once they are ready, spread the mix-ins evenly in the casserole dish. If your dish is prone to sticking, you can grease it or use a silicone baking mat.
- In a bowl, whisk together the eggs, Greek yogurt, salt and pepper until smooth.12 large eggs, 1 and ½ cups Greek yogurt, ½ teaspoon fine sea salt
- Pour the egg mixture over the mix-ins in the casserole dish. Stir gently to evenly distribute and coat everything.
- Bake at 350 °F for 35-45 minutes or until the center is fully set and no longer jiggly. It will puff up as it bakes but deflate shortly after taking it out of the oven.
- Remove from the oven and let the casserole sit for 10–15 minutes before slicing. This helps it firm up and makes it easier to slice.
- Enjoy warm or see the notes below for storing for later.
Notes
Meal Prep for the Week: After resting, slice it into portions and store in airtight containers in the fridge for up to 4 days. You can store multiple squares in the same container if you like. Then simply reheat when you are ready.
To Freeze: This casserole freezes beautifully. Let it cool fully in the fridge lightly covered with the lid slightly ajar to limit moisture buildup. Once cold, portion into containers and freeze for up to 3 months.
I recommend placing it in the refrigerator the night before you plan to eat it (and up to 2 days in advance), though it can be reheated from frozen too (I just find that it can reheat a bit unevenly that way and take a bit longer).
Reheating: Microwave until warmed through (about 45-90 seconds depending on the microwave). You can also use the oven: preheat to 350°F and bake the casserole or portion that you're reheating for 15-20 minutes or until heated through.
*Mix-Ins: Nearly anything goes in this casserole (veggies, meat, cheese, bread)- see the above post for lots of ideas! Just keep in mind that you don't want your mix-ins to be too watery (or the casserole may not set). It is also important to note that things like meat or hard vegetables like potatoes need to be cooked ahead of time.
Larger Casserole: If you would like to bake this in a 9x13 inch pan instead, you can add up to 6 cups of mix ins (but keep the eggs/yogurt the same). The bake time may vary slightly with the wider dish so keep an eye on it after 30 minutes.
**Nutrition calculated without mix-ins.
Nutrition
Calories: 186kcal | Carbohydrates: 3g | Protein: 19g | Fat: 11g | Saturated Fat: 3g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 4g | Trans Fat: 0.003g | Cholesterol: 376mg | Sodium: 336mg | Potassium: 199mg | Fiber: 0.04g | Sugar: 3g | Vitamin A: 523IU | Calcium: 106mg | Iron: 1mg
Nutrition Note: Nutritional information is estimated using an online calculator and accuracy is not guaranteed. Remember food is more than numbers and this info is intended as a support.
Tried this recipe?Please comment and tell me what you thought!
Marie says
This is so simple yet tasty and reheats really well!