1. In a food processor, puree the chipotles, garlic, oil, and salt. Wipe the chickens with paper towels. Thoroughly coat the pieces on all sides with a layer of the chipotle paste.
2. Place in a nonreactive baking dish or in resealable bags and refrigerate for 2 hours, or as long as overnight.
3. Heat the grill to medium. With the lid open, grill the chicken on both sides until well marked but not burned—about 7 minutes per side. Turn the heat to low, close the lid, and cook the chicken, skin side up, until an instant-read thermometer inserted in the thickest part of the thigh reads 165 degrees. (Alternatively, bake at 350 degrees for approximately 30 to 40 minutes.)