Combine wine, oil, garlic, oregano, salt and pepper and set aside.
Cut steak into strips, 2"x1/4" wide, or as thin as possible
Pout wine marinade over beef strips, and let stand for 1 hour at room temperature. Drain meat strips and cook, in 2 batches, in hot butter, stirring for 2 to 3 minutes on all sides.
Serve meat in a chafing dish or on a hot tray to keep warm.
Open one end of pita to make a pocket. Set out dishes of lettuce, tomato, cucumber and yogurt. Allow each person to fill their own pita.