12 Egg Casserole Recipe: High-Protein Breakfast for Crowds

This 12-egg casserole recipe transforms breakfast into a crowd-pleasing meal that bakes up fluffy, golden, and packed with protein—perfect for busy mornings or brunch gatherings.

The secret lies in whisking eggs to ribbons and folding in cheesy, savory fillings before baking at 350°F for 25-30 minutes, ensuring a tender, custardy texture with crispy edges. I developed this after testing countless versions, and it consistently delivers restaurant-quality results without requiring fancy techniques.

What sets this recipe apart is its versatility—swap in vegetables, meats, or cheeses to suit any dietary preference, from classic ham and cheese to veggie-packed versions with spinach and feta.

The high-protein formula makes it ideal for meal prep, keeping everyone fueled for hours. Plus, it’s designed to feed 8-10 people, so you’ll never scramble to feed a crowd again.

The result is a foolproof dish that’s creamy, rich, and satisfying—each bite delivers a perfect balance of eggy custard and your choice of fillings. The one-dish convenience means minimal cleanup, while the customizable fillings let you adapt it to any taste or dietary need.

Whether you’re hosting brunch or prepping for the week, this casserole delivers big flavor with minimal effort.

Serve it warm with fresh fruit or a crisp green salad for a complete meal, or pack leftovers for grab-and-go breakfasts. The 30-minute bake time ensures you’ll have dinner on the table quickly, without sacrificing taste or texture. Here’s how to make it—simple, reliable, and always impressive.

Ingredients for 12 egg casserole

Twelve eggs, a handful of pantry staples, and 30 minutes—this casserole feeds crowds without the fuss.

The eggs are non-negotiable here—room temperature is key for even baking. Grab the largest eggs you can find at Costco or your local grocery store's bulk section—they yield more custard. For the cheese, sharp cheddar melts best, but Monterey Jack works too if you prefer milder flavor. Pre-shredded cheese has anti-caking agents that can make the casserole gummy, so grate your own if possible. The ham can be any cut—black forest or honey ham add sweetness, but regular deli ham works perfectly fine for a savory version.

No spinach? Swiss chard or kale in equal amounts will work, but chop them extra fine—they cook down significantly. Out of bell pepper? Zucchini or mushrooms add moisture and heartiness. The cream is crucial for that rich, custardy texture, but Greek yogurt at half the amount cuts calories without sacrificing creaminess. For a veggie-packed version, boost the spinach to 8 oz and add 1 cup diced tomatoes. The garlic powder can be swapped for 1 tsp fresh minced garlic if you're feeling fancy—just add it directly to the egg mixture.

Prep ahead for maximum convenience—assemble the casserole the night before and refrigerate. It'll be even more flavorful after sitting overnight. Bake in a 9x13-inch baking dish for best results. Leftovers keep for 4-5 days in the fridge, and portions reheat beautifully in the microwave or oven. For meal prep, divide into individual servings and freeze for up to 3 months. The texture holds up perfectly—just add a splash of milk when reheating if it seems dry.

Step-by-step instructions for 12 egg casserole

Here's how to create a protein-packed breakfast that feeds a crowd in record time.

In a large skillet over medium heat, melt 0.5 cup butter until it foams. Add the finely chopped yellow onion and cook for 3-4 minutes until soft and translucent. This is your flavor foundation—don't rush it.

Add the diced red bell pepper and diced ham, stirring occasionally for 5 minutes until the peppers soften slightly and the ham begins to brown. The ham will release its savory juices, which will infuse the entire casserole. Remove the skillet from heat and let it cool for 5 minutes—this prevents the eggs from scrambling when mixed in later.

In a separate large bowl, whisk together the 12 whole Large Eggs until no streaks remain. Add the 1.5 cups heavy whipping cream and whisk again until fully combined. This step is critical—properly emulsifying the eggs and cream ensures a silky texture throughout the casserole.

Gradually whisk in the 0.25 cup all-purpose flour until smooth, then add the 3 cups shredded sharp cheddar cheese, 1 tsp salt, 0.5 tsp black pepper, and 1 tsp garlic powder. Mix until the cheese is evenly distributed and no dry spots remain. Here's the thing—freshly grated cheese melts more smoothly, so if your cheese is pre-shredded, pulse it in a food processor to break up any anti-caking agents.

Gently fold the sautéed vegetable and ham mixture into the egg mixture, taking care not to overmix. Add the 5 oz chopped fresh spinach and stir until just combined—you want the spinach to be evenly distributed but still visible throughout the casserole. The spinach will wilt slightly as it cooks, adding vibrant color and nutrients.

Transfer the mixture to a greased 9x13-inch baking dish, spreading it evenly. Tap the dish gently on the counter a few times to remove any air bubbles—this ensures an even bake. The casserole should look thick but pourable, with a smooth surface that's ready for the oven.

Preheat your oven to 350°F and place a baking sheet on the lower rack to catch any drips. Bake the casserole for 45-50 minutes until the top is golden brown and the center is just set—it should still have a slight jiggle when gently shaken. Here's where it gets fun: the edges should pull away from the baking dish slightly, indicating it's ready.

For the final touch, broil on high for 1-2 minutes until the top is deeply golden and slightly crispy. Watch it closely—broilers can be aggressive! Remove from the oven and let it rest for 5 minutes before slicing. This resting period allows the casserole to set properly, making it easier to serve and preventing a runny texture.

Use a sharp knife to cut the casserole into 10 equal squares, serving immediately while still warm. Each portion should be rich and creamy with a crispy top, packed with protein from the eggs and ham, and vibrant from the vegetables. The sharp cheddar adds a tangy depth that balances the savory ham and creamy texture.

For best results, serve with a side of fresh fruit or a simple green salad to balance the richness. This casserole reheats beautifully, so leftovers can be portioned and frozen for quick breakfasts later in the week. The secret to its success lies in the proper balance of ingredients and the gentle baking process—no scrambling, no overmixing, just a perfectly set, protein-packed breakfast for your whole crowd.

Serving suggestions for this 12 egg casserole

Classic Brunch Sides

Serve your casserole with a fresh fruit platter featuring seasonal berries like strawberries, blueberries, and sliced peaches. The natural sweetness cuts through the richness of the eggs and cheese beautifully. I like to arrange them on a wooden board with a drizzle of honey for an elegant touch. 🍓

A crisp green salad with a light vinaigrette balances the hearty casserole perfectly. Toss mixed greens with sliced cucumbers, cherry tomatoes, and a dressing of olive oil, lemon juice, and Dijon mustard. Add toasted walnuts for crunch and texture contrast.

Warm Bread Pairings

Warm biscuits or cornbread make an ideal pairing—they soak up any extra custard beautifully. I recommend baking a batch of sourdough biscuits with honey butter for dipping. For a gluten-free option, try almond flour biscuits that hold up well to the creamy casserole.

Beverage Recommendations

A strong cup of coffee is the classic choice—its bitterness complements the richness of the eggs and cheese. For a brunch twist, serve chai latte or matcha tea with a splash of milk. Both add warmth and a subtle sweetness that enhances the meal.

Make-Ahead Serving

For meal prep, portion leftovers into airtight containers and store in the fridge for up to 5 days. Reheat individual servings in the microwave for 1-2 minutes until warm. I like to pack these for quick grab-and-go breakfasts during busy weeks.

Holiday Brunch Upgrade

Transform this into a festive brunch by adding crispy bacon or sausage links on the side. Garnish the casserole with fresh chives or parsley for a pop of color. Serve with sparkling juice or mimosas for a celebratory touch. 🥂

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