Bring a large pot of lightly salted water to a boil. Break or cut vermicelli into 5cm pieces and cook for 8 to 10 minutes or until al dente; drain.
Spread pasta in a 20x30cm baking dish that has been greased with vegetable spray or butter. In a bowl combine milk, eggs, garlic salt, parsley, pepper and 1 cup of the mozzarella. Pour over the pasta and sprinkle with the parmesan cheese.
Bake for 15 minutes. Reduce heat to 180. Pour spaghetti sauce over pasta, top with pepperoni and remaining mozzarella. Cook until cheese is completely melted; about 10 minutes.