Pre-heat oven to 375°F. Place vegetables in colander in sink. Cook macaroni as directed on package. Pour over vegetables in colander to drain and quickly thaw vegetables. Return macaroni and vegetables to same saucepan.
Add packaged cheese sauce, milk and dressing; mix well. Add tuna and 1/2 cup of the cheddar cheese; mix well.
Spoon into 2-qt. round casserole dish; cover with foil. Bake 35 min. or until heated through. Uncover; top with remaining 1/2 cup cheddar cheese. Bake an additional 3 to 4 min. or until cheese is melted.
1 (12 oz.) can of chicken can be used instead of tuna.