Position knife blade in food processor bowl. Combine first 6 ingredients in processor bowl. Process until smooth. Set aside 1/4 cup tomato mixture.
Place chicken in a large heavy-duty, zip-top plastic bag. Pour remaining tomato mixture over chicken. Seal bag; turn bag to coat chicken. Marinate in refrigerator 8 hours.
Coat grill rack with cooking spray; place on grill over medium-hot coals (350° to 400°). Remove chicken from marinade, discarding marinade. Coat tomato halves with cooking spray. Place chicken and tomato halves on rack; grill, covered, 5 to 6 minutes on each side or until chicken is done and tomato is cooked but still slightly firm. Place chicken on 4 individual serving plates; top each chicken breast half with 1 tablespoon reserved tomato mixture. Arrange 2 grilled tomato halves on each plate with chicken.
To mince garlic in the food processor, drop it through the food chute with the processor running and process until it's minced. Than add other ingredients to chop.
Cooking Light Low-Fat, Low-Calorie Quick and Easy Cookbook