In a small bowl, whisk together the lemon zest, juice, rosemary, oil, salt and pepper. Put the marinade in a large zip baggie. Add the chicken to the marinade and let marinate at room temperature. Turn the bag occasionally.
GRILL THE CHICKEN:
Prepare the grill to medium heat. Lightly oil the grates. Remove the chicken from its marinade. Place the chicken on the grill, cover and cook until lightly browned. Turn the chicken and cook on the other side until cooked through (total time 8 to 10 minutes).