Cut left over pizza into bite sized squares and arrange in the baking dish.
Mix eggs, cooked sausage, milk, mozzarella cheese, onion, butter, garlic, oregano, and salt together in a large bowl.
Pour over pizza pieces.
Top with Parmesan cheese and red pepper flakes.
Cover dish with aluminum foil.
Bake for 45 minutes.
Remove foil and continue baking until eggs are set and Parmesan cheese is melted, about 20 more minutes.
Serve hot.
Notes
StorageThis breakfast pizza recipe is best consumed hot out of the oven. However, you can store the leftovers—if you have any leftovers, that is!Cover the dish with aluminum foil or plastic wrap, or transfer the casserole to an airtight container. Refrigerate for up to three days.This casserole also freezes well for up to 3 months.To reheat:Microwave individual portions in short increments of time, checking often until it's warmed up. Eggs can get tough if they're overcooked, so reheat carefully!Tips
Freeze the Mozzarella before shredding.
Don't use pre-shredded cheese! It has a coating on it that keeps it from melting right. Take an extra 2 minutes and shred it yourself.
Quickly cut the leftover pizza into bite-sized pizza squares with a large, heavy chef's knife. You can also use a pizza cutter if you have one!
The casserole is finished when the egg mixture is set, meaning it no longer jiggles in the center. Give the casserole dish a gentle nudge to check, first. It will read 160F on an instant-read thermometer when you stick it in the middle. Or, stick a toothpick in the center and look for raw egg.
You can prep this easy pizza breakfast casserole ahead of time. Simply assemble the layers and cover the casserole dish with foil. Refrigerate until you want to bake.
If you use a 9"x13" casserole dish, the mixture will be thinner and require less cook time. Watch it closely to avoid overcooking. I do recommend a square, 9"x9" pan for best results.