1. Whisk together olive oil, lemon juice, minced garlic, salt and pepper. Then add the diced onion.
2. Transfer marinade to a gallon sized plastic bag or container and add the chicken. Place in the fridge and marinate overnight.
3. Place the chicken on a preheated grill and sprinkle with pepper. Cook for about 20 minutes or until cooked through, with no pink in the center.
4. Grill additional lemon slices, for garnish.
5. Serve and enjoy!
