1. Combine yogurt, shredded cucumber, tahini, 1 tablespoon lemon juice, and garlic in a small bowl; set aside.
2. Combine remaining 2 teaspoons lemon juice, olive oil, and next 4 ingredients (through chicken) in a small bowl. Heat a grill pan over medium-high heat. Thread chicken pieces evenly onto 4 (8-inch) skewers. Coat grill pan with cooking spray. Add chicken to pan; cook 10 minutes or until done, turning every 2 minutes. Remove chicken from skewers.
3. Divide chicken evenly among pita halves. Fill each pita half with 2 tablespoons lettuce, 1 tablespoon onion, 2 cucumber slices, 2 tomato slices, and 1 tablespoon sauce.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.