In a medium mixing bowl, whisk together Greek yogurt, olive oil, lemon juice, minced garlic, dried oregano, ground cumin, smoked paprika, salt, and black pepper until well combined. Add the chicken thighs to the bowl, ensuring each piece is well coated with the marinade. Cover the bowl with plastic wrap or a lid and refrigerate for at least 30 minutes.
Heat a large, non-stick skillet over medium heat. Once hot, add the marinated chicken thighs. Cook for approximately 7-8 minutes on each side, or until golden brown and cooked through (internal temperature should reach 165°F/75°C). Transfer the chicken to a plate and let it rest for 5 minutes before slicing into strips.
Without cleaning the skillet, add the diced cucumber, diced tomato, and thinly sliced red onion. Season with a pinch of salt and pepper. Sauté the vegetables over medium heat for about 3-4 minutes, stirring occasionally, until slightly softened while still maintaining a crisp texture.
While the vegetables are sautéing, warm the whole wheat pita breads in a dry skillet over low heat or microwave for about 15-20 seconds until soft and pliable.
To assemble, cut the rested chicken thighs into strips. Take a warmed pita and fill it with a generous portion of the sautéed vegetables. Top with the sliced chicken, sprinkle crumbled feta cheese, and garnish with fresh chopped parsley.
Serve the gyros immediately while warm, accompanied by extra Greek yogurt on the side for dipping or drizzling.
Notes
Serve the gyros on a wooden board or platter for a rustic look, with a side of lemon wedges for an extra zing.