In medium bowl, mix chicken, dressing, chili powder and lime peel. Spread chicken mixture over half of each tortilla. Sprinkle with cheese and green onions. Fold tortilla over filling and press down. Brush tops with oil.
Place quesadillas, oil sides down, on grill. Brush tops with remaining oil. Cover grill. Cook 4-6 minutes, turning once, until both sides are golden brown and cheese is melted.
Remove from grill, cut into wedges and serve with sour cream, if desired.