Photo via Flickr User terren in Virginia
Place butter, C&C Herbes de Provence, and salt in small bowl; mash with fork until blended to thick granular paste. Starting at neck end of each chicken, carefully run fingers under skin of breasts to loosen. Rub herb-seasoned butter on chicken under loosened skin and on outside of each chicken. Truss chickens by tying legs together and tying wings flush to sides.
Let chickens stand at room temperature about 30 minutes before cooking.
Remove spit from rotisserie attachment and prepare barbecue (medium-high heat). Thread chickens on spit, pushing close to centre. Reattach spit to motor. Place shallow disposable foil pan(s) under chickens for drips.
Cook chickens until thermometer inserted into thickest part of thigh registers 170°F, about 50 minutes. Turn off grill, but do not open. Let chickens rest in covered grill 10 minutes.