Preheat oven to 400ºF. Rinse turkey inside and out. Pat dry. In small bowl, combine butter, minced garlic, salt and pepper. Loosen skin of turkey and rub butter between skin and meat. Place lemons and onion inside cavity of turkey. Tie legs with kitchen string. Combine 2 cups of BBQ sauce, soy sauce, and bay leaf in saucepan. Simmer 30 minutes to blend flavors. Discard bay leaf. Set aside until ready to use.

Place turkey on rack in heavy, large roasting pan. Roast one hour then reduce heat to 325ºF. Brush turkey with BBQ sauce. Roast 20 minutes. Brush with BBQ sauce every 20 minutes, about 1 hour 10 minutes longer, for a total of 2 1/2 hours until meat thermometer inserted into thickest part of thigh registers 175 degrees. If turkey begins to get too brown, cover with foil while roasting.

Transfer turkey to platter. Cover loosely with foil and let rest 30 minutes before slicing. Serve immediately with remaining cup of BBQ sauce.