Warm & Satisfying Creamy Mushroom & Herb Breakfast Casserole

Is there anything better than a warm, savory breakfast that feels like a hug on a plate? You know, the kind of dish that fills your kitchen with the most incredible aroma and gathers everyone around the table. This Creamy Mushroom & Herb Breakfast Casserole is exactly that. It’s the perfect solution for a lazy weekend brunch or a make-ahead morning that’s entirely fuss-free. Honestly, it might just become your new favorite way to start the day.

Top Reasons To Make It

This casserole is truly a dream for busy mornings. It’s a complete meal all by itself, packed with protein and savory flavor. You can prepare it the night before and just pop it in the oven when you wake up. Plus, it’s incredibly forgiving—swap ingredients based on what you have in your fridge! It’s a crowd-pleaser for a breakfast buffet and a guaranteed win for anyone looking for healthy food ideas that don’t skimp on comfort.

Ingredients

• 1 tablespoon olive oil (for sautéing)
• 1 small yellow onion, diced (for a sweet, savory base)
• 16 ounces cremini mushrooms, sliced (for deep, earthy flavor)
• 3 cloves garlic, minced (for a little pungent kick)
• 10 large eggs (the hearty base of the casserole)
• 1 cup whole milk (makes the egg mixture wonderfully rich)
• 1/2 cup grated Parmesan cheese (adds a salty, nutty flavor)
• 1 cup shredded sharp cheddar cheese (for that classic, melty goodness)
• 1 teaspoon dried thyme (for a warm, herbal note)
• 1/2 teaspoon smoked paprika (adds a touch of smokiness)
• 1/2 teaspoon salt, plus more to taste
• 1/4 teaspoon black pepper
• Butter or non-stick spray (for greasing the baking dish)

Instructions

1. Preheat your oven to 350°F (175°C) and generously grease a 9×13 inch baking dish.
2. Warm the olive oil in a large skillet over medium heat. Add the diced onion and cook for about 4-5 minutes, until it becomes soft and translucent.
3. Add the sliced mushrooms to the skillet. Cook, stirring occasionally, for 8-10 minutes until they have released their liquid and turned a beautiful golden brown. Add the minced garlic and cook for one more minute, until fragrant. Remove the skillet from the heat and let it cool slightly.
4. In a very large bowl, whisk the eggs and milk together until they are completely combined and a little frothy.
5. Stir in the Parmesan cheese, half of the cheddar cheese, thyme, smoked paprika, salt, and pepper into the egg mixture.
6. Gently fold the slightly cooled mushroom and onion mixture into the egg base until everything is evenly distributed.
7. Pour the entire mixture into your prepared baking dish. Sprinkle the remaining cheddar cheese evenly over the top.
8. Bake for 40-45 minutes. You’ll know it’s done when the edges are golden brown and the center is completely set (no jiggle when you gently shake the pan).
9. Let the casserole rest for about 5-10 minutes before slicing and serving. This helps it set perfectly!

Creamy Mushroom & Herb Variations & Substitutions

The beauty of this recipe is how easily you can make it your own. For a veggie boost, stir in a couple of handfuls of fresh spinach with the mushrooms. If you’d like a different protein, some diced smoked turkey sausage is a fantastic addition. Don’t have cheddar? Try Gruyère or Monterey Jack for a different melty cheese experience. To make it gluten-free, just ensure all your other ingredients are certified GF—this recipe is naturally gluten-free!

Casserole Baking Instructions

For the perfect bake, position a rack in the center of your oven and preheat thoroughly. Using a glass or ceramic dish is ideal for even heating. The key doneness cue is a fully set center. If you find the top browning too quickly, you can loosely tent it with a piece of aluminum foil for the last 10-15 minutes of baking.

Serving Ideas & Pairings

This casserole is a star on its own, but it also plays well with others. For a full breakfast buffet, serve it alongside a platter of fresh fruit, crispy roasted potatoes, or a simple green salad. A dollop of sour cream or a sprinkle of fresh chives on top right before serving is just divine. So good. It pairs wonderfully with a fresh cup of coffee or a bright glass of orange juice for the ultimate morning breakfast ideas.

Storage & Reheating

Leftovers? Let the casserole cool completely, then cover it tightly or store slices in an airtight container. It will keep in the refrigerator for up to 4 days. To reheat, simply warm individual portions in the microwave for 60-90 seconds until hot. For a larger piece, reheat it in a 350°F oven for about 15-20 minutes, covered with foil to prevent drying out. You can also freeze this casserole! Wrap slices well and freeze for up to 2 months. Thaw overnight in the fridge before reheating.

Frequently Asked Questions

• Can I make this casserole ahead of time? Absolutely! This is one of the best simple breakfast ideas for make-ahead meals. Assemble the entire casserole, cover it, and refrigerate overnight. In the morning, just bake it as directed—you might need to add 5-10 extra minutes to the baking time since it will be cold from the fridge.
• What’s the best way to reheat it without drying it out? The microwave is quick and easy for a single serving. For the best texture, the oven is my go-to. That low, slow heat brings back its creamy, moist texture perfectly.
• I’m not a mushroom fan. What can I use instead? No problem! This is a great base for all sorts of savory breakfast ingredients. Try swapping the mushrooms for chopped bell peppers, broccoli florets, or even sun-dried tomatoes for a different flavor profile.