To assemble the gyros, place a pita into the center of a square of foil. One pita per piece of foil. Spread 1/4 cup of the tzatziki evenly, keeping 1 inch away from the edges on all 6 pitas.
Place the chicken, onions, tomatoes and lettuce in a line going down the middle of the pita. Top with feta and olives. You’re going to divide all the ingredients equally between the 6 gyros. Wrap up the gyro by folding both sides of the pita up over the filling and wrapping the foil tightly around the gyros.
To eat, peel back the foil in stages. If you’re going to save for later, place in the refrigerator. Enjoy!