Whisk salad dressing, garlic powder, and salt together in a shallow baking dish; add chicken breasts and turn to coat. Cover the dish with plastic wrap and marinate in the refrigerator, 4 hours to overnight.

Preheat an outdoor grill for high heat and lightly oil the grate.

Remove chicken from marinade and shake off excess; discard remaining marinade.

Cook chicken on the preheated grill until no longer pink in the center and the juices run clear, about 7 to 8 minutes on each side. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).