Cut 2 thin slices from lemon; set aside. Squeeze 2 teaspoons lemon juice from remaining lemon into small bowl. Add rosemary, salt, pepper, oil and garlic; mix well.
Add chicken breast halves; turn to coat. Arrange chicken on broiler pan. Top each with lemon slice.
Broil 4 to 6 inches from heat for 5 minutes. Turn chicken, placing lemon slices under chicken. Broil an additional 5 to 7 minutes or until chicken is fork-tender and juices run clear. Discard lemon slices.