Heat oven to 375. Lightly spray a 9" x 13" casserole dish w/ cooking spray. Cook macaroni as directed, drain, transfer to casserole dish.
Place frozen squash and milk in a saucepan. Cook over low heat, stirring until defrosted, increase heat to medium. Cook, stirring until almost simmering.
Remove pan from heat. Stir in cheddar cheese, monterey cheese, ricotta cheese, salt, mustard and cayenne pepper. Stir well. Pour over macaroni, stir to combine. In bowl, combine bread crumbs, parmesan cheese and oil. Sprinkle over casserole. Bake until bubbly, 20 mins, put under broiler for 3 mins for a nice crust.