Place fajita seasoning mix in gallon-size resealable food-storage plastic bag. Place vegetables in bag; seal. Shake vegetables until evenly coated.
In 12-inch nonstick skillet, heat oil over medium-high heat. Add vegetables; cook and stir, scraping any seasoning mix from bottom of skillet, 3 to 4 minutes or until vegetables are almost crisp-tender. Stir in chicken and barbecue sauce. Cook and stir 2 to 3 minutes longer or until chicken and sauce are heated through.