Preheat oven to 375°F (190°C) and grease a 9×13-inch baking dish.
In a skillet, cook turkey sausage over medium heat until browned; drain excess fat.
Add diced onion and garlic to the same skillet; sauté until softened (3-5 minutes).
Stir in spinach and cook until wilted (2-3 minutes); set aside.
In a bowl, whisk eggs, cream of mushroom soup, oregano, paprika, salt, and pepper.
Add cooked sausage mixture, spinach, and 1.5 cups cheese to the egg mixture; combine thoroughly.
Transfer to the prepared baking dish, top with remaining cheese, and bake 35-40 minutes until golden.
Let rest 10 minutes before slicing into 8 portions.