In a medium bowl, mix the pineapple juice, vegetable oil, soy sauce, brown sugar, garlic powder, and pepper. Place chicken in the bowl, and coat with the mixture. Cover, and marinate in the refrigerator at least 2 hours.
Preheat the oven broiler.
Place chicken on a baking sheet. Broil 5 minutes on each side in the preheated oven, or until no longer pink and juices run clear. Discard remaining marinade.