Spread olive oil in a cast iron skillet or large baking dish; set aside. Cook spaghetti according to package directions. Drain spaghetti. In a large bowl, stir together spaghetti, Marinara Sauce, onion, pepper, mushrooms, black olives, pepperoni, and diced chicken. Pour into cast iron skillet or baking dish. Top with Mozzarella Cheese and sprinkle with Parmesan Cheese. Bake at 350-degrees for 30 minutes or until bubbly and lightly browned.