Heat 1 tablespoon of the oil in large skillet on medium-high heat. Add chicken; cook and stir 3 minutes or until lightly browned. Remove from skillet.
Heat remaining 1 tablespoon oil in same skillet. Add onion and bell pepper; cook and stir 3 to 5 minutes. Return chicken to skillet. Add water and Seasoning Mix; cook and stir 3 minutes or until heated through.
Spoon into warm tortillas. Serve with assorted toppings, if desired.