Clean hens inside and out, removing gizzard pack. Cut bird lengthwise in half.
In a large, shallow dish, place hens skin-side up. Pour orange/pineapple juice, dressing, garlic powder, salt and pepper. Refrigerate and marinade for 2-4 hours.
Coat grill with oil and preheat to 350°F to 400°F. Remove hen halves from marinade and pat dry with paper towels. Place bird halves skin-side up on grill and cook on each side for approximately 10-15 minutes, when internal temperature reaches 165°F degrees on a meat thermometer placed in thigh.