Chickens are juicier when barbecued whole instead of cut up.
Rinse the chickens inside and out under cold water, and pat dry. Truss legs with kitchen twine, and set aside.
Heat a charcoal or gas grill. If using a charcoal grill, arrange hot coals around inside edge of grill. Arrange chickens, breast sides up, in a row across the center. If using a gas grill, cook chickens over medium heat. Cook until brown on all sides, rotating every 5 to 7 minutes; cover grill as needed to maintain heat.
Baste chickens with barbecue sauce. Continue cooking, basting frequently, until an instant-read thermometer registers 170 degrees in breast and 180 degrees in thickest part of the thigh (avoiding bone), about 1 hour. If chickens brown too quickly before they are cooked through, transfer to baking pans and finish in a 350 degree oven.