Add the minced garlic, apple cider vinegar, lemon juice, olive oil, Greek yogurt, oregano, salt, and black pepper to a large zip-top bag or non-reactive container.

Add the chicken thighs and massage or toss until every piece is completely coated.

Cover or seal and refrigerate for at least 2 hours. For deeper flavor, marinate for 3–12 hours. Avoid marinating for longer than 24 hours.

Cut the cucumbers in half lengthwise and use a teaspoon to scrape out the watery seeds.

Coarsely grate enough cucumber to produce approximately 1/2–3/4 cup after draining.

Place the grated cucumber inside a clean kitchen towel or several layers of paper towel. Squeeze firmly to remove as much excess moisture as possible.

Transfer the cucumber to a bowl. Add the Greek yogurt, lemon juice, olive oil, garlic, salt, and black pepper.

Stir until combined, then refrigerate for at least 20 minutes to allow the flavors to develop.

Combine the diced tomatoes, cucumbers, red onion, and parsley in a bowl.

Season lightly with salt and black pepper and toss gently.

Preheat an outdoor grill to medium-high and lightly oil the grates. Alternatively, heat a small amount of oil in a large skillet over medium-high heat.

Remove the chicken from the marinade, allowing excess marinade to drip away.

Cook the chicken thighs until deeply golden on both sides and completely cooked through. Depending on thickness, this will generally take several minutes per side.

Make sure the thickest part of each chicken thigh reaches an internal temperature of 165°F (74°C).

Transfer the chicken to a clean plate. Cover loosely and rest for about 5 minutes.

Slice the chicken into strips or bite-sized pieces.

Warm the pita breads or flatbreads until soft and pliable.

Place fresh salad down the center of each pita.

Add generous portions of sliced chicken and spoon homemade tzatziki over the top.

Fold or roll the pita around the filling and serve the Greek Chicken Gyros Recipe immediately.