In a large skillet, brown beef and onion until meat is no longer pink; drain. Stir in the enchilada sauce, tomatoes, olives, salt, garlic powder and pepper; bring to a boil. Reduce heat; simmer, uncovered, for 20 minutes.
In a small bowl, combine cottage cheese and egg; set aside. Spread one-third of the meat sauce in a greased 13-in. x 9-in. baking dish. Top with half the Monterey Jack cheese, half the cottage cheese mixture and half the tortillas. Repeat layers, ending with meat sauce. Sprinkle with cheddar cheese.
Cover and bake at 350° for 20 minutes. Uncover and bake 10 minutes longer or until bubbly and cheese is melted.