Prepare filling by mixing cooked chicken, sour cream, onions and 1/4 cup of each cheese.
Spread 1/2 cup green sauce on bottom of baking pan and warm remaining sauce in pan over low heat.
Heat tortillas in a pan over medium heat until soft. Dip in warm sauce, remove immediately, and place in baking tray. Spread 1/2 cup of filling in each tortilla.
Wrap tortillas around filling and place seam side down in prepared baking pan. Cover all enchiladas with remaining sauce and remaining cheese. Top with chopped olives.