SPRINKLE both sides of chicken breasts with garlic salt.
HEAT oil in Dutch oven or large saucepot on medium-high heat. Add chicken; cook 1 to 2 minutes on each side or until browned on both sides. Remove from pan; set aside. Add 3 cups water to pan. Bring to boil. Stir in Shell Macaroni; top with chicken. Reduce heat to medium-low; cover. Simmer 12 minutes or until shells are tender.
STIR in tomato and Cheese Sauce. Reduce heat to medium-low; cook until cheese sauce is melted and mixture is heated through, stirring occasionally.