Name: High Protein Veggie Breakfast Casserole Recipe
Prep time: 15 min
Cook time: 35 min
Total time: 50 min
Cuisine: American
Ingredients: ½ medium Vidalia onion, diced (or yellow/white onion); 1 red pepper, membrane removed, seeded, and diced; 1 medium zucchini, ends removed and diced; 1 small yellow squash, ends removed and diced; 2 cloves garlic, minced; 6 oz fresh baby spinach; 4 oz sharp cheddar cheese, shredded from block; 4 large eggs; 32 oz liquid egg whites; 2 tbsp light cream; 1 tbsp avocado oil (or olive oil); Avocado oil cooking spray (or olive oil spray), as needed; 1 tsp salt; ¼ tsp black pepper

Jump to Recipe· 3.9 from 84 reviews

If you’re looking for a vibrant, nourishing way to kickstart your mornings, this High Protein Veggie Breakfast Casserole Recipe is an absolute game-changer. Bursting with fresh vegetables, creamy cheese, and packed with egg-based protein, it’s perfect for anyone who loves a hearty breakfast without the heaviness. Whether you’re feeding a family or prepping meals ahead, this casserole brings savory, colorful flavors together in one satisfying dish that fuels your day with ease and delight.

Ingredients You’ll Need

A white bowl filled with three layers of diced vegetables: the bottom layer has light yellow zucchini cubes, the middle layer has dark green zucchini pieces with a soft texture, and the top layer has bright red bell pepper and translucent white onion pieces mixed evenly throughout. A wooden spatula rests on the right inside edge of the bowl, all set against a white marbled surface. photo taken with an iphone --ar 4:5 --v 7

Gathering the right ingredients is the secret to any outstanding recipe, and this casserole is no different. Each item is carefully chosen to add a perfect balance of taste, texture, and nutrition to the dish.

Avocado oil cooking spray or olive oil spray: For greasing the baking dish and keeping everything from sticking while adding a subtle richness.
1 tbsp avocado oil or olive oil: To sauté the veggies and bring out their natural sweetness.
½ medium Vidalia onion (diced): Adds a mild, sweet flavor that softens beautifully when cooked; yellow or white onions work well too.
1 red pepper (membrane removed, seeded, diced): Brings a pop of color and a touch of crisp sweetness to the mix.
1 medium zucchini (ends removed, diced): Offers mellow freshness and tender texture.
1 small yellow squash (ends removed, diced): Adds subtle sweetness and a splash of sunny color.
2 cloves garlic (minced): Provides that warm, aromatic punch that elevates all the flavors.
6 oz fresh baby spinach: Adds vibrant green color, a boost of nutrients, and a mild earthy taste once wilted.
4 oz sharp cheddar cheese (shredded from block): Melts into creamy pockets of flavor that make every bite irresistible.
4 large eggs: The protein powerhouse binding everything together.
32 oz liquid egg whites: Adds extra protein without heaviness and keeps the casserole light and airy.
2 tbsp light cream: Just enough creaminess to enrich the egg base without overpowering the veggies.
1 tsp salt: Enhances and balances all the flavors.
¼ tsp pepper: Adds a gentle kick and depth.

How to Make High Protein Veggie Breakfast Casserole Recipe

Step 1: Prepare your oven and baking dish

Start by preheating your oven to 375 degrees Fahrenheit. While it heats up, spray a 9×13 baking dish generously with avocado oil or olive oil cooking spray. This ensures your casserole comes out perfectly without sticking and gets a nice golden crust on the edges.

Step 2: Sauté your colorful vegetables

Warm 1 tablespoon of avocado or olive oil in a large skillet over medium heat. Toss in the diced onion, red pepper, zucchini, and yellow squash. Sauté gently for about 8 to 10 minutes, stirring occasionally, until the vegetables soften and their natural sweetness comes alive. This step is crucial because it unlocks amazing flavors and softens the veggies just right before baking.

Step 3: Layer the sautéed veggies in the baking dish

Evenly spread the softened veggies along the bottom of your prepared baking dish. This creates a vibrant, veggie-packed base for the casserole, giving every bite a fresh crunch and a burst of garden-fresh taste.

Step 4: Wilt the garlic and spinach

Give your skillet a quick spray with oil, then add the minced garlic and fresh baby spinach. Stir constantly until the spinach just wilts—this gentle cooking preserves its vivid color and tender, delicate flavor. Once ready, spread the garlic-spinach mixture evenly over the sautéed veggies in your dish.

Step 5: Add cheese and egg mixture

Sprinkle shredded sharp cheddar cheese generously on top of the spinach layer. Then, whisk together the large eggs, liquid egg whites, light cream, salt, and pepper until blended and frothy. Pour this rich mixture slowly over the layered veggies and cheese, soaking everything for a perfect custardy texture after baking.

Step 6: Bake until golden and set

Place the casserole in your preheated oven and bake for 35 to 40 minutes. You’ll know it’s ready when the eggs are completely set, the cheese turns lightly golden, and the whole dish smells like pure breakfast magic. Allow it to cool for a few minutes before slicing into 4 hearty servings.

How to Serve High Protein Veggie Breakfast Casserole Recipe

A rectangular white ceramic baking dish filled with a baked egg dish showing two main layers: the top layer is golden-yellow with patches of melted orange cheese, scattered wilted dark green spinach leaves visible throughout. The edges of the dish are slightly browned and crispy, with the mixture looking soft and fluffy inside. The dish sits on a white marbled surface accompanied by a light beige cloth on the side. photo taken with an iphone --ar 4:5 --v 7

Garnishes

A sprinkle of fresh herbs like chopped parsley or chives adds a bright pop of color and fresh flavor that takes this casserole to the next level. You can also add a dollop of Greek yogurt or a light avocado salsa for creamy contrast and beneficial fats.

Side Dishes

This casserole stands out on its own but pairs wonderfully with crisp mixed greens, roasted cherry tomatoes, or a fresh fruit salad for balance. If you’re feeling indulgent, serve alongside some crusty whole-grain toast to soak up those cheesy, eggy edges.

Creative Ways to Present

For a personalized twist, try baking this casserole in individual ramekins for single servings. This makes a fun presentation for brunch guests. Another idea is to use colorful mini bell peppers as vegetable bowls and scoop the casserole inside for a festive, bite-sized treat.

Make Ahead and Storage

Storing Leftovers

Once cooled, cover any leftover casserole tightly with aluminum foil or transfer to an airtight container. It keeps well in the refrigerator for up to 3 to 4 days, perfect for quick breakfasts or snacks throughout the week.

Freezing

This casserole freezes beautifully, making it a perfect meal prep staple. Wrap portions individually or store the whole dish in a freezer-safe container for up to 3 months. Just remember to thaw overnight in the fridge before reheating.

Reheating

Reheat leftovers gently in the oven at 350 degrees Fahrenheit for about 15 minutes or until warmed through. You can also microwave single servings, but using the oven helps retain that lovely texture and flavor without drying out the eggs.

FAQs

Can I use other vegetables in this High Protein Veggie Breakfast Casserole Recipe?

Absolutely! Feel free to swap or add your favorite veggies like mushrooms, broccoli, or kale. Just make sure to sauté them first to remove excess moisture and maintain the casserole’s perfect texture.

Is this casserole suitable for meal prep and freezing?

Definitely! This dish is fantastic for meal prepping since it stores well in the fridge and freezes without losing flavor or texture, making healthy breakfasts easy to grab and go.

What can I substitute for liquid egg whites if I don’t have any?

You can replace liquid egg whites with additional whole eggs or egg substitutes, but keep in mind it may change the casserole’s calorie count and texture slightly, making it denser and richer.

Can I make this recipe dairy-free?

Yes! Simply swap the sharp cheddar cheese for a dairy-free cheese alternative or omit it entirely. Use an oil spray or dairy-free cream to keep the dish creamy and flavorful without dairy.

How do I know when the casserole is fully cooked?

The casserole is done when the eggs are completely set and no longer jiggly in the center. The cheese on top should be lightly golden, and you can test doneness by inserting a toothpick in the middle – it should come out clean.

Final Thoughts

All in all, this High Protein Veggie Breakfast Casserole Recipe is a delicious and nutritious way to power up your morning with vibrant veggies and satisfying protein. It’s straightforward to make, endlessly adaptable, and perfect for sharing or meal prepping. I truly hope you give this recipe a try and find it as comforting and energizing as I do – it just might become your new favorite breakfast tradition!