In a bowl whisk together the 1/2 cup of olive oil, pineapple juice, juice of one lime, brown sugar, cumin, chili powder, 1 tablespoons of salt and 1 tablespoon pepper. Reserve ¼ cup of marinade and set aside.
Cover chicken in marinade, mixing until well coated. Use a zip top bag or plastic wrap covered bowl. Refrigerate 1 - 2 hours.
Prepare a grill fire to 350° using hickory or pecan for smoke flavor. Toss onions and bell peppers with 2 tablespoons olive oil, 1/2 teaspoon of salt and 1/2 teaspoon pepper.
Add a griddle or cast iron skillet to the grill and add the onions and bell peppers. Cook, stirring occasionally for about 5 minutes.
Remove the chicken from the marinade and add to the grill with the vegetables. Cook with the grill closed about 10 minutes.
Stir the fajita mixture and add the reserved cup of marinade. Continue to cook with the grill closed until vegetables are cooked through and chicken reaches 165° using a digital thermometer.
Remove from grill to a serving platter.
Serve immediately with warmed tortillas, shredded cheese, sour cream, salsa, lime slices and cilantro.