It's all about pickle brine! Notice that they serve the 1/2 chicken, potato chips and pickles (and a roll) and that is because they are using gallons of dill-based pickle juice (not sweet pickles) and pepper for the brine. When there a few years ago, I asked about their method. Marinate chicken halves in pickle juice and lots of pepper overnight, place on grill at indirect medium flame (around 350F) and cook slowly for about 1.5 to 2 hours. Boil down the pickle juice reserve to about 1/2, add salt and about 1/2 cup margarine, and brush chicken generously throughout the grilling period. When pulled off the grill, put cooked chicken in a deep pan and pour the rest of the brine-butter mixture over it to soak until served. Let me know how you make out! I am making this for a big party today!
I followed the recipe exactly and there seemed to be an absence of fullness to the sauce so I added about 1/2 tsp. garlic powder and 1 tsp. of onion powder and it is most excellent. We'll see if the family agrees!