Heat the meatballs on the stove top with red pepper flakes and oregano. Heat the pita breads in the oven on low heat until warm. Once heated, place 2-3 meatballs in each pita bread. Top with feta, mozzarella and parmesan cheeses. As cheese begin to melt, top off with lettuce, onion and black olives. Serve “taco style” for a snack or main meal.