In a large freezer bag, combine red wine vinegar, Worcestershire sauce, vegetalbe oil, and minced garlic cloves. Place steak in bag, seal, and shake to coat. Lable and freeze. Bundle wtih 6 pita breads.
When ready to prepare, thaw steak in marinade. Thaw pita breads. Make cucumber sauce by mixing peeled, shredded cucumber with the yogurt. Chill until ready to serve. Grill thawed meat on the grill or under the broiler until medium rare. Slice steak against the grain into thin strips. Warm and open the pitas. Stuff with steak and shredded lettuce. Top with cucumber sauce.