Cut chicken into 1 inch cubed pieces. Place in a gallon size zip-top bag.
Pour margarita mix over the chicken in the bag, add salt and pepper.
Seal the bag and move chicken around to make sure it is coated with marinade.
Place the bag in a bowl or dish and put in refrigerator.
Refrigerate for 30 minutes up to 6 hours.
If using wooden skewers, make sure to soak in water prior to use.
Cut peppers and onion to 1 inch chunks.
Thread chicken and vegetables on skewers, alternating chicken and vegetables.
Heat the grill to medium-high heat.
Oil the grill (I use cooking spray) and place skewers on the grill.
Cover and cook until not pink. About 5 minutes on each side.
Remove chicken from grill and place on serving plate. Sprinkle with Mexican seasoning and chopped cilantro.