Whisk the extra virgin olive oil, lemon juice, garlic, 1 ¾ teas salt, 1 teas pepper, ¾ teas cayenne, parsley, basil, oregano, and cilantro in a bowl. Arrange chicken quarters in a large resealable bag and pour marinade over (reserve ½ cup for basting). Seal and move chicken around to cover and coat. Let marinate for 8 to 12 hours.
When ready to cook, prepare a wood or wood / charcoal fire in a large grill for indirect heat. Add a small pan filled with water. Top with the grate and lid and allow to come to around 300 degrees.
Remove the chicken from the marinade and place skin side up, on the side opposite the hot coals. Cover and cook for 45 minutes. Flip and baste the chicken with the reserved marinade. Cook for another 45 minutes, or until the chicken temps at 175 F. (you may have to watch your heat to make sure it remains hot enough while cooking)
Remove the chicken from the grill and wrap in foil. Allow to rest for 10 minutes.
Meanwhile, rub the onion and scallions with olive oil. (Tip, I use a toothpick to hold my onion slices together while grilling) Season with salt, pepper and a pinch of cayenne. Grill the onions until charred, about 4 minutes per side and the scallions about 2 minutes.
Remove to a tray.
Rub the avocado flesh side with olive oil and season as well. Grill until charred, about 1 - 3 minutes.
Serve the chicken quarters and grilled veggies with lime wedges and allow guests to squeeze them over their platters.