In a food processor, combine the onion, scallions, chiles, garlic, five-spice powder, allspice, pepper, thyme, nutmeg and salt. Process to a coarse paste. With the machine on, add the the soy sauce and oil in a steady stream. Pour the marinade into a couple ziploc bags, add the chicken and turn to coat. Refrigerate 8 to 12 hours.
Bring the chicken to room temperature before grilling.
Grill the chicken over a medium-high fire, turning about every 10 minutes, until well browned and cooked through, 35 to 40 minutes. Transfer the chicken to a platter and serve.