Preheat oven to 375. Place vegetables in colander in sink. Cook macaroni as on the package.
Pour vegetables in colander to drain and quickly thaw vegetables.
Return macaroni and vegetables to same saucepan. Add cheese Sauce, milk and mix well. Add tuna and 1/2 cup of the cheddar cheese; mix well. Spoon into 2-qt. casserole dish; cover with foil.
Bake 35 min. or until heated through. Uncover; top with remaining 1/2 cup cheddar cheese. Bake and additional 3 to 4 min. or until cheese is melted.