Spray a large nonstick skillet with the cooking spray.
Heat over medium heat until hot. Add chicken tenders.
Cook 7-10 minutes until browned and no longer pink in the middle. Cool slightly.
Combine chicken, tomato, cucumber, sliced olives, feta cheese and onion in a medium-sized bowl. Drizzle with vinger and oil and toss to coat. Sprinkle with oregano, salt, and mint if using. Toss to combine.
Place lettuce leaf into each pita half. Divide chicken mixture evenly and spoon into each pita pocket.