COOK chicken in 2 Tbsp. of the dressing in large skillet on medium-high heat 5 minutes, stirring occasionally. Reduce heat to medium.
STIR in remaining dressing, the tomato and seasoning mix. Cook and stir 5 minutes or until chicken is cooked through.
PLACE chips on large serving platter; top with layers of lettuce, chicken mixture, cheese, olives and onions.