Sourdough & Sausage Breakfast Casserole

If you’re looking for a hearty, make-ahead breakfast casserole that actually stands out from the rest, this Sourdough and Sausage Breakfast Casserole is it. The tangy sourdough bread, savory sausage, and rich mushroom topping come together in a way that feels just a little more special than your typical egg bake.

This recipe makes a full 9×13 pan, serving about 12 people, which makes it perfect for holidays like Christmas morning, weekend guests, or spring brunches like Mother’s Day. Best of all, it’s prepped the night before, so all you have to do in the morning is pop it in the oven.

I have had this breakfast sausage and egg casserole recipe on my website for a long time. It was first posted back in 2011, and it’s one I make often. However, the photos were terrible, and the post was written about everything under the sun, except maybe sausage breakfast casseroles.  So today it gets a glow up! New photos, updated recipe card with nutritional information, and more! 

Sausage Breakfast Casserole Recipe

This isn’t your average breakfast casserole. The sourdough adds a subtle tang that balances the richness of the sausage and cheese, while the creamy mushroom topping gives it that cozy, comfort food feel. It’s hearty without being boring, and it holds up beautifully for serving a crowd. Plus, that overnight rest means less stress in the morning and more time enjoying coffee with your people.

Ingredients in Sourdough Bread Breakfast Casserole

• Sourdough bread – The star of the show. Adds structure and that signature tangy flavor that sets this apart. Use stale bread or fresh bread; either works. Homemade sourdough bread or store-bought works just fine!
• Cheddar cheese – Melts into the layers for richness and that classic breakfast casserole flavor
• Bulk breakfast sausage – Brings savory, slightly spicy flavor and protein to make it filling
• Red pepper flakes – A little kick to balance the richness (adjust to taste)
• Dry mustard – Adds depth and enhances the flavor of the cheese and eggs
• Eggs – The base that holds everything together
• Milk – Keeps the casserole soft and custardy instead of dry
• Green onions – Fresh flavor and a little bite to brighten things up
• Cream of mushroom soup – Creates that creamy, comforting topping layer
• Fresh mushrooms – Add texture and earthy richness that pairs perfectly with sausage
• Additional milk – Thins the topping so it spreads easily
• Cherry tomatoes (optional) – A fresh, bright garnish that balances the richness

How to Make Sourdough and Sausage Breakfast Casserole

Start by greasing a 9×13 baking dish.

Layer the sourdough bread slices across the bottom of the pan, using just enough to fully cover the surface. Sprinkle the shredded cheddar cheese evenly over the bread.

In a skillet, brown the sausage with the red pepper flakes, breaking it up into small crumbles as it cooks. Drain any excess grease and let it cool slightly. Spread the sausage evenly over the cheese layer.

In a large bowl, whisk together the eggs, dry mustard, 2 ¼ cups milk, and green onions.

Pour this mixture evenly over the casserole.

Cover and refrigerate overnight (or at least 6–8 hours).

When ready to bake, preheat the oven to 350°F.

In a separate bowl, stir together the cream of mushroom soup, 1/3 cup milk, and fresh mushrooms.

Pour this mixture evenly over the casserole. Add the remaining cheese.

Bake uncovered for 50–60 minutes, or until the center is set and the top is lightly golden.

Let the casserole rest for 5–10 minutes before slicing. Garnish with cherry tomatoes if desired, then serve.

Make Ahead + Storage

Make Ahead: Assemble the casserole the night before, cover tightly, and refrigerate. Bake fresh in the morning.

Storage: Store leftovers covered in the refrigerator for up to 3 days.

Reheating: Reheat individual portions in the microwave or warm larger portions in the oven at 300°F until heated through.

Love it? Pin it!

If you can’t wait to make this sourdough breakfast bake recipe, be sure you can find it! Pin it to your favorite Pinterest recipe board before you go. 

Tips for Success

• Use slightly stale sourdough for the best texture
• Don’t skip the overnight rest; it helps the bread soak up all that flavor
• If the top starts browning too quickly, loosely tent with foil toward the end
• Letting it rest before cutting makes for cleaner slices

FAQs – Overnight Breakfast Casserole

Can I make this without the overnight step? You can, but letting it sit gives the best texture. If you’re short on time, let it rest at least 30–60 minutes before baking.

Can I use a different bread? Yes, but sourdough really gives this casserole its signature flavor. French bread would be your next best option.

Can I add vegetables? Absolutely. Bell peppers or spinach would be great additions.

This is one of those recipes that proves breakfast casseroles don’t have to be boring. The sourdough and sausage combination gives it just enough of a twist to make people ask for the recipe, and the make-ahead factor makes it one you’ll come back to again and again.

This recipe was originally posted on August 12, 2011. It has been updated to improve user experience and reshared on May 4, 2026.

I couldn’t delete the photos of my sweet doggies that were in the post, though!

My sweet Gabby and Sully. <3