If you're using frozen fries, cook fries according to package directions. In the last 5 minutes of cooking time, add the grilled chicken to the baking sheet with the fries.
Top fries with chicken, dollops of tzatziki and crumble with feta.
Notes
To make these greek fries vegetarian, replace the chicken with white beans, chickpeas, or sliced tempeh.The ready to eat grilled chicken is usually found with the packaged salads and meals in the produce section at Trader Joe's.