Mix Seasoning Mix, orange juice, oil and vinegar in small bowl until well blended. Place chicken in large resealable plastic bag. Add marinade; turn to coat well. Refrigerate 30 minutes or longer for extra flavor.
Heat large nonstick skillet on medium-high heat. Remove chicken from marinade. Discard any remaining marinade. Add chicken to skillet; cook and stir 8 minutes or until cooked through.
Serve chicken in warm tortillas with desired toppings.