Tenderize or butterfly your chicken to ensure it is even thickness and place into a large ziplock bag.
Combine all the marinade ingredients into a big bowl, then pour it over the chicken. Give everything a good mix in the bag to make sure the chicken gets covered with the marinade. Let it sit in the fridge for at least 2 hours before you cook it on the grill.
Slice your vegetables into thin strips and place into a bowl. Cover with oil and garlic salt.
Set the grill temperature to about 400°F (medium-high) and put a little oil on the grill grates so the food doesn't stick.
Take each chicken piece out of the marinade and let any extra marinade drip off. Put the chicken on the grill and stay close by. It'll take around 16-18 minutes to cook the chicken through. Make sure to turn the chicken a couple of times while cooking. Watch over the chicken and shift it around the grill as needed. The goal is to get a bit of char on each side of the chicken.
When the chicken is cooked, put it on a big plate and loosely cover it with aluminum foil. Give it about 10 minutes to rest before you cut into it. Place a flat iron skillet right on the grill. It'll take roughly 10 minutes, so just shift it around as needed.
When the peppers and onions are nearly finished cooking, slice the chicken into small strips that you can easily bite. Push the veggies to one side of the skillet and put in the chicken. Squeeze some fresh lime juice over it all and take it right to the table. Remember, the iron skillet is really hot, so use gloves to handle it.
These fajitas are good to go, perfect for sharing with your family. Grab the warm tortillas, sour cream, and whatever other toppings you like.