In a medium-sized mixing bowl, combine the sliced chicken breast, minced garlic, dried oregano, ground cumin, paprika, salt, black pepper, olive oil, and lemon juice. Stir thoroughly to ensure that the chicken is well-coated with the marinade. Cover and refrigerate for a minimum of 30 minutes; for optimal flavor, marinate for up to 2 hours.
Preheat your grill or skillet over medium-high heat. Once hot, add the marinated chicken strips. Cook for approximately 5-7 minutes, or until the chicken is cooked through and has developed a slight char, stirring occasionally to ensure even cooking. Remove the chicken from the heat and let it rest for a moment.
In a separate mixing bowl, combine the Greek yogurt with the finely diced cucumber. Stir until thoroughly mixed. Season with salt and pepper to taste, adjusting to your preference.
Lightly toast the whole wheat pita breads on the grill or in the skillet for about 1 minute on each side, or until they are soft and pliable, making them easier to wrap.
Take a warm pita and place a generous portion of the cooked chicken strips in the center. Then top with the diced tomatoes, thinly sliced red onion, and a hearty dollop of the tzatziki sauce.
Sprinkle freshly chopped parsley on top for a burst of color and flavor. Carefully wrap the pita around the filling to secure everything inside and serve immediately for the best taste experience.
Notes
Serve the gyros on a wooden board or plate, accompanied by extra tzatziki sauce in a small bowl for dipping. Garnish with lemon wedges for added freshness.