How to Make It
Light a grill using 6 pounds of charcoal briquettes or 8 pounds of hardwood charcoal. When the flames have died down and the coals are white on the outside, divide the coals in half and push to each side of the grill, leaving the center empty. Top each pile of coals with half of the rosemary sprigs.
Season the chicken inside and out with a good amount of salt and pepper. Fold the wing tips under the back and tie the legs together. Set the chicken in the center of the grill, breast side up. Cover the grill and cook the chicken without turning for about 50 minutes, or until an instant-read thermometer inserted in the thickest part of a thigh registers 160°. Transfer the chicken to a carving board and let it rest for 10 minutes.
Heat the oil in a large skillet. Add the arugula and stir over moderately high heat just until wilted, about 1 minute. Season with salt and pepper. Spread the arugula on a platter. Carve the chicken and arrange on the wilted arugula; serve with the Quick Pickled Pearl Onions.
Such a simple recipe relies on using a good quality chicken—preferably one that is antibiotic free. It is worth paying more for a pasture-raised chicken that spent time outdoors because it has the most flavor.