Preheat oven to 375 degrees. In a large cast iron skillet place chicken leg quarters, onions, and garlic. Drizzle with olive oil, sprinkle with coarse salt and freshly ground black pepper.
Bake uncovered at 375 degrees for 40-45 min. Baste chicken with pan drippings a couple of times if desired. Increase oven temperature to 400 degrees and bake for another 10-15 minutes for a nice crispy skin.
Alternatively, to check chicken for doneness, insert an instant read digital thermometer into the thigh area, making sure to avoid touching the bone. The internal temperature should read 180 degrees for a leg quarter (170 degrees for breasts, and some say 165 degrees in general for all chicken). If unsure, make sure juices run clear and not pink.