Preheat oven to 350 degrees F and prepare a baking dish with non-stick cooking spray and set aside.
Ground and cook sausage in a skillet until fully cooked. Add garlic and onions to the skillet and sauté with sausage for 2 minutes. Place this in your prepared baking dish. Add chopped spinach and 1/4 cup mozzarella, parmesan, and 1/4 provolone.
In a separate bowl whisk eggs with salt and pepper. Pour egg wash into baking dish and gently mix to make sure eggs are covering the entire dish. Top with remaining mozzarella and provolone cheese and bake for 45 minutes or until a fork can come out clean and eggs are cooked all the way through.