In a medium-sized bowl, whisk together balsamic vinegar, garlic, rosemary, black pepper, salt, and olive oil. Add chicken, coating evenly allowing chicken to marinate at least 15 minutes.
Place chicken (skin side up) in a baking dish, distributing any remaining marinade over the breasts. Bake for 25-30 minutes or until internal temperature reaches 170° F. Serve and enjoy!