Place all marinade ingredients into the food processor and pulse until everything has broken up and there are no more chunks.
Place the blended marinade into a large plastic bag, add the chicken, and let marinate for 4 hours (up to 24). *Optional: Reserve ¼ cup of the marinade for fajitas as a topping or as a final brush on the grill before you marinade.
For the Grilled Chicken:
Preheat Grill: Prepare the grill, targeting 400 – 450 degrees Fahrenheit, using the two-zone method of grilling (or direct/indirect). Place a grill-safe skillet over direct heat to warm up with the grill (we use cast iron).
Prep Chicken: Remove chicken from the marinade. Discard the marinade.
Grill Chicken: Grill the chicken over direct heat for 5 minutes with the lid closed, then flip and continue grilling direct another 5 minutes. At this point, you should have a nice crust on the chicken, but the inside isn’t close to done yet.
Grill Peppers and Onions: While the chicken is grilling over direct heat, add olive oil to the pan and then add the onions and peppers. Stir occasionally and remove when they are soft.
Finish Chicken Over Indirect: Move the chicken to indirect heat and finish until the internal temperature of the chicken reaches 160 – 165 degrees Fahrenheit. Usually, about the time we move the chicken to indirect heat, the onions and peppers are done and we remove them also from grill.
Slice and Serve: Slice the chicken and then add back to the pan with peppers and onions for serving.
For the Fajitas:
Warm up your tortillas, and serve them with the chicken, pepper, and onion mixture, and your favorite toppings and sides.