In a mixing bowl, combine olive oil, oregano, garlic powder, paprika, salt, pepper, and lemon juice. Add chicken strips and marinate for at least 30 minutes.

Preheat the grill to medium-high heat. Grill the marinated chicken for about 5-7 minutes on each side or until fully cooked.

In a bowl, mix together Greek yogurt, grated cucumber, minced garlic, olive oil, dill, lemon juice, and salt until well combined. Refrigerate until ready to serve.

Warm the pita bread on the grill for a minute. Place grilled chicken on the pita, top with tzatziki sauce, mixed greens, tomato slices, and red onion. Roll up and serve.