Step 1

Remove sausage from casings. In a skillet over medium-high heat, cook sausage until cooked through and crumbly. Drain and set aside.

Step 2

Wipe skillet with a paper towel to remove sausage drippings. Add butter to skillet and melt over medium heat. Add onion and mushrooms; cook until tender, about 3 to 4 minutes.

Step 3

In a large bowl, whisk together eggs, milk, Italian seasoning, salt, and pepper. Add sausage, onions, and mushrooms. Stir in mozzarella, Parmesan, and tomatoes.

Step 4

Pour egg mixture into a 13x9" baking pan coated with non-stick cooking spray. Bake, uncovered, at 400 degrees until set and a bit puffed in the center, about 35 - 40 minutes.

Step 5

Remove from oven and let stand 5 minutes before serving. Sprinkle top with chopped parsley.

Step 6

Italian Egg Casserole may be prepared the night before, refrigerated over night, and baked the next morning. Increase baking time to 45 - 50 minutes.