Place the marinade ingredients in a glass bowl and stir to mix. Add the chicken to the glass bowl and flip with tongs to coat the chicken in the marinade. Marinate for at least 2 hours, preferably 3 hours, ideally 12 hours and no longer than 24 hours.
Make the Greek Salad by combining the tomatoes, onions, cucumber, feta cheese, oregano salt and pepper. Toss with olive oil
Cook Chicken
Brush the outdoor grill with oil, then preheat on medium high. Or heat 1 tablespoon of oil in a grill pan over medium high heat.
Remove chicken from marinade. Cook the chicken for 5 to 7 minutes on each side, until golden brown and cooked through (cooking time depends on size of chicken).
Remove the chicken from the grill / pan onto a plate. Cover loosely with foil and allow to rest for 5 minutes before serving.
Assemble Gyros
Place a warmed pita bread on a piece of parchment paper (or you could use foil). Place sliced chicken on pita, then top with Greek Salad and tzaziki sauce.
Roll the wrap up, enclosing it with the parchment paper. Twist the end with the excess parchment paper to secure it.