In a large ziploc bag, combine chicken, olive oil, lemon zest, lemon juice, garlic, parsley, salt, and pepper.
Seal the bag and shake it all up until well combined.
Place bag in the refrigerator and marinate for about 4 hours or overnight.
Preheat the grill to about 375F to 400F.
Brush grill grates with olive oil.
Remove chicken breasts from marinade and place them on the hot grill; cook without touching it until the chicken breasts start getting some grill marks, about 5 minutes.
Turn the chicken breasts over, cover the grill, and let finish cooking, about 7 more minutes, depending on the thickness of the chicken. Chicken is done when a meat thermometer registers 165 degrees Fahrenheit.
Remove chicken from grill; cover and let rest for 5 minutes before cutting.
TO PREPARE ON A CAST IRON GRILL PAN
Preheat oven to 350.
Grease a grill pan with cooking spray and set it over medium-high heat.
Add chicken pieces and cook for 4 minutes; flip, and continue to cook for 2 more minutes, or until lightly browned.
Place grill pan in the oven and cook for 18 to 20 minutes, or until chicken is cooked through.
Remove from oven and let rest 5 minutes.