Cook sausage in sauté pan; drain, remove from pan and set aside.
Reserve 1 tablespoon drippings in sauté pan. Add green and red diced peppers; cook until crisp-tender retaining bright color. Stir in red pepper flakes and drained sausage.
Lightly spray 1/2 steam table pan with vegetable spray. Pour macaroni and cheese and sausage mixture into pan, stirring gently to mix all ingredients evenly. Bake at 350°F for 30 to 40 minutes or until heated to 165°F and top is lightly browned.