Lay the chicken breasts in a shallow baking dish large enough to place them in a single layer without overlapping.
1½ pounds boneless skinless chicken breasts
Peel and lightly crush the garlic, then cut the rosemary sprig into 3 pieces. Distribute the rosemary and garlic around the chicken pieces.
3 medium cloves garlic, 1 sprig fresh rosemary
Add the lemon juice and olive oil to the baking dish, then season the chicken with salt and pepper.
¼ cup freshly squeezed lemon juice, 2 tablespoons olive oil, Salt, freshly ground black pepper
Turn the chicken pieces over and let them stand at room temperature for about 45 minutes or in the refrigerator for at least 2 hours.
Preheat the grill or heat a grill pan on the stove until very hot.
Place the chicken breasts on the grill and cook for 8 minutes.
Flip the chicken, then pour the marinade over it.
Continue grilling until the chicken is cooked through, about 6 to 8 more minutes depending on how thick the pieces are.