Step 1: Marinate the Chicken

1. Prepare the Marinade: In a medium-sized bowl, whisk together Greek yogurt, olive oil, lemon juice, minced garlic, dried oregano, salt, and pepper until well combined.
2. Marinate the Chicken: Add the chicken strips to the marinade, ensuring they are evenly coated. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, allowing the flavors to infuse. For best results, marinate overnight.

Step 2: Prepare the Tzatziki Sauce

1. Grate the Cucumber: Using a box grater, grate the cucumber, then squeeze out the excess water using a clean kitchen towel or cheesecloth.
2. Mix Ingredients: In a separate bowl, combine Greek yogurt, grated cucumber, minced garlic, olive oil, lemon juice, salt, and pepper. Mix well.
3. Adjust and Chill: Taste the sauce and adjust seasoning as needed. Garnish with freshly chopped dill and refrigerate until ready to serve.

Step 3: Cook the Chicken

1. Preheat the Grill or Skillet: Heat a grill pan or skillet over medium-high heat. Lightly oil the surface to prevent sticking.
2. Grill the Chicken: Remove chicken strips from the marinade, letting any excess drip off. Place the strips on the grill or skillet and cook for 5-7 minutes per side, or until the chicken is fully cooked and golden brown. Internal temperature should reach 165°F (74°C).

Step 4: Assemble the Gyros

1. Warm the Pita: Lightly toast the pita bread on the grill or in a skillet for 1-2 minutes on each side, until soft and warm.
2. Fill the Pita: Place a portion of grilled chicken strips in the center of the pita. Add diced tomatoes and shredded lettuce for a fresh crunch.
3. Top with Tzatziki: Spoon a generous amount of tzatziki sauce over the chicken and vegetables.
4. Garnish and Serve: Sprinkle with freshly chopped parsley and serve immediately.