In a large skillet, cook the beef, pepperoni, onion and green pepper over medium heat until meat is no longer pink; drain. Stir in mushrooms; set aside.
Combine vermicelli and butter in a greased 13x9-in. baking dish; toss to coat. Pour 1 cup tomato sauce over pasta; top with half of meat mixture. Combine Swiss and mozzarella cheeses; sprinkle half over top. Sprinkle with oregano and basil. Layer with remaining meat and cheese mixtures. Pour remaining tomato sauce over top.
Bake, uncovered, at 350° for 25-30 minutes or until bubbly.