In a large, resealable plastic bag combine the marinade ingredients, including 2 tablespoons oil. Place the chicken in the bag, press the air out of the bag, and seal tightly. Turn the bag to distribute the marinade, place the bag in a bowl, and refrigerate for 3 to 5 hours, turning occasionally.
Prepare the grill for direct cooking over medium heat (180° to 230°C).
Brush the cooking grates clean. Brush the onion slices with oil. Remove the chicken from the bag and discard the marinade. Season the chicken evenly with the salt and pepper, and then grill over direct medium heat, with the lid closed, until the meat is firm to the touch and no longer pink in the center, 8 to 12 minutes, turning once. At the same time, grill the onions over direct medium heat until tender, 12 to 15 minutes, turning once or twice. Remove from the grill as they are done, and let the chicken rest for 3 to 5 minutes.
Cut the chicken crosswise into slices about 12 millimeters thick. Serve warm with the onions.
All of our recipes are created by our expert chefs at the Weber Grill Academy. View more inspirational recipes or book a course at the Grill Academy now.