Winter Brunch Egg Casserole

My sister found this recipe during that first snowstorm we spent in her tiny apartment, when the kitchen was the only warm room in the place. We doubled everything because her roommate kept wandering in with a hopeful look and a coffee mug. Now it is the first thing I make whenever the temperature drops below freezing and someone says they are coming over.

Last winter I brought this to a potluck where everyone forgot to bring serving utensils. We ended up passing around the entire dish with one giant spoon, and somehow that made it taste even better. Someone asked for the recipe before they even finished their first bite.

Ingredients

• 1 medium onion, diced: Sweet onions work beautifully here and become even sweeter as they slowly soften in the pan
• 1 red bell pepper, diced: The red variety adds such lovely color and natural sweetness that green peppers just cannot match
• 1 cup baby spinach, chopped: It wilts down to almost nothing but adds such a fresh green note that cuts through all the richness
• 1 cup cremini or white mushrooms, sliced: Cremini mushrooms have such a deeper, earthier flavor than plain white button mushrooms
• 1 ½ cups shredded cheddar cheese: Sharp cheddar gives you that perfect punch while still melting into creamy perfection
• 1 cup whole milk: Whole milk creates such a velvety custard and low-fat versions just leave you with a rubbery texture
• ½ cup heavy cream: This is what makes the custard feel like something from a fancy brunch spot
• 8 large eggs: Room temperature eggs will incorporate so much more smoothly into the dairy mixture
• 4 cups rustic bread, cut into 1-inch cubes: Day-old sourdough or French bread holds up beautifully without turning to mush
• 1 tsp salt: Season carefully since both the cheese and any optional meat will add their own saltiness
• ½ tsp black pepper: Freshly cracked pepper adds such a nice warmth that the pre-ground kind lacks
• ½ tsp dried thyme: Thyme pairs so naturally with eggs and cheese that it just makes the whole dish sing
• ¼ tsp smoked paprika: This adds such a subtle smokiness that people notice but cannot quite identify
• ½ cup cooked breakfast sausage or bacon, crumbled: A little goes such a long way if you want to add some meaty depth
• 2 tbsp chopped fresh parsley: This bright green garnish makes everything look fresh and inviting

Instructions

Get your oven ready:

Preheat oven to 350°F and generously butter a 9x13-inch baking dish so nothing sticks later.

Sauté the vegetables:

Cook onion and bell pepper for about 5 minutes until they soften, then add mushrooms for 3 more before wilting in the spinach.

Whisk the custard:

Beat eggs, milk, cream, and seasonings until completely combined and slightly frothy.

Combine everything:

Gently fold bread cubes, cooked vegetables, half the cheese, and meat if using into the egg mixture until evenly coated.

Assemble the casserole:

Pour everything into your prepared dish and scatter the remaining cheese across the top.

Bake until golden:

Bake for 40 to 45 minutes until the center is set and the top is beautifully browned.

Rest before serving:

Let it cool for 10 minutes so the custard sets up properly, then garnish with parsley.

Save

This became my go-to for those mornings when everyone is still in pajamas and nobody wants to go out in the cold. Something about it baking makes the whole house smell like comfort and possibility.

Make It Ahead

I have learned through many rushed mornings that this casserole actually benefits from sitting overnight in the refrigerator. The bread has more time to soak up the custard and the flavors meld together beautifully. Just add about 5 minutes to the baking time if it goes into the oven cold.

Serving Ideas

A simple arugula salad with lemon vinaigrette cuts through the richness perfectly. Sparkling apple cider feels festive and the bubbles cleanse your palate between bites.

Make It Your Own

This recipe is incredibly forgiving and welcomes whatever you have in your refrigerator. Leftover roasted vegetables work beautifully and different cheeses change the character entirely.

• Try Gruyère for a fancy French twist
• Add diced ham if you want something milder than sausage
• Swap spinach for kale in the middle of winter

Save

There is something so generous about a dish that feeds six people and makes the house smell wonderful. Serve it warm and watch how quickly it brings everyone to the table.

Recipe FAQs

→ Can I prepare this casserole the night before?

Absolutely. Assemble the entire dish, cover tightly, and refrigerate overnight. Let it sit at room temperature for 30 minutes before baking as directed.

→ What type of bread works best?

Rustic breads like sourdough, French, or Italian baguette hold up beautifully. Slightly stale or day-old bread absorbs the custard better without becoming mushy.

→ Can I make this dairy-free?

Substitute whole milk with unsweetened oat or almond milk, and replace heavy cream with canned coconut milk or full-fat coconut cream. Use your favorite dairy-free shredded cheese.

→ How do I know when it's done baking?

The center should feel set when gently shaken, not jiggly. The top will be golden brown, and a knife inserted near the center should come out clean.

→ Can I add meat to make it non-vegetarian?

Certainly. Crumbled cooked breakfast sausage, bacon, or diced ham work wonderfully. Cook the meat first and drain excess fat before adding to the mixture.

→ What vegetables can I substitute?

Diced zucchini, bell peppers of any color, kale instead of spinach, or roasted sweet potato cubes all work beautifully. Aim for about 3 cups total vegetables.