Preheat oven to 400° & prepare baking sheet by spreading 1 tablespoon olive oil evenly.
In a large bowl combine turkey, egg, breadcrumbs, Pecorino Romano cheese, pepper, garlic powder, onion, mushrooms, parsley, and oregano. Mix well. Gently shape with hands, 1 1/2 inch diameter meatballs and place on greased baking sheet spaced slightly apart. Bake meatballs at 400° F for 20-25 minutes turning once so the meatballs are browned on both sides. Meatballs are cooked at 165°F.
In a medium size saucepan add marinara sauce and warm over medium heat. Once meatballs are cooked through in the oven, add them to the sauce on the stove top. Heat in sauce an additional 10 minutes. Serve.
Serving size: 5 meatballs, Calories: 285 calories, Fat: 13 grams, Saturated fat: 3.5 grams, Carbohydrates: 15 grams, Sugar: 2 grams, Sodium: 285 milligrams, Fiber: 2 grams, Protein: 33 grams, Cholesterol: 115 milligrams