Combine cherries, onion, sage, salt and thyme; mix well. Cut a pocket on the thicker side of the chicken breast; sprinkle lightly with salt if desired. Stuff 1/4 of cherry mixture into the pocket; close opening with metal skewers or wooden picks. Combine oil, vinegar, garlic salt and pepper; mix well. Marinate stuffed chicken breasts 1/2 hour in refrigerator. Broil or grill chicken breasts, brushing with marinade, until fully cooked and juices run clear when sliced.
Oven Method: Brown stuffed chicken in oven-safe skillet on both sides. Bake at 375° F 12 to 15 minutes or until juices run clear.