Place lamb strips in a heavy-duty, zip-top plastic bag. Combine vinegar and next 6 ingredients, stirring well. Pour vinegar mixture over lamb; seal bag, and shake until meat is well coated. Marinate in refrigerator at least 8 hours.
Combine yogurt and next 3 ingredients. Cover and chill. Remove lamb from bag; discard marinade. Coat a nonstick skillet with cooking spray; place over medium-high heat until hot. Add lamb; cook 2 to 3 minutes or until browned, stirring frequently. Drain and pat dry with paper towels.
Place 1 lettuce leaf on each pita round; place half of lamb on each. Top each with 2 tablespoons tomato and half of yogurt mixture. Sprinkle with green onions. Roll up pita rounds and serve.