01 - In a large mixing bowl, combine Greek yogurt, olive oil, lemon juice, minced garlic, oregano, ground cumin, paprika, salt, and black pepper. Whisk until evenly blended.
02 - Place chicken breasts in the bowl and coat thoroughly with the marinade. Cover and refrigerate for at least 1 hour or overnight for optimal flavor absorption.
03 - Preheat grill, grill pan, or skillet over medium-high heat. Remove chicken from marinade and cook for 5–7 minutes per side, or until internal temperature reaches 165°F. Transfer to a cutting board and allow to rest for 5 minutes.
04 - Cut cooked chicken into thin strips across the grain for tender, bite-sized pieces.
05 - Heat pitas briefly on the grill or in a dry skillet until soft and pliable.
06 - Layer shredded lettuce, sliced cucumber, tomato, onion, and chicken strips onto warmed pitas. Top generously with tzatziki sauce.
07 - Fold pitas and serve immediately, garnished with additional fresh herbs if desired.