In a large mixing bowl combine 1 1/4 cups flour and salt. Cut in shortening until pieces are the size of small peas. Sprinkle cold water, 1 tablespoon at a time, over mixture, tossing with a fork after each addition until all is moistened. Form dough into a ball. On a lightly floured surface, flatten dough with hands. Roll dough from center to edges, forming a circle about 12 inches in diameter.
Ease pastry into a 10-inch tart pan with a removable bottom or a 10-inch quiche dish. Press pastry into fluted sides of tart pan or quiche dish and trim edges. Line the unpricked pastry shell with a double thickness of foil. Bake in a 450 degree F oven for 8 minutes. Remove the foil. Bake for 4 to 5 minutes more or until pastry is set and dry. Remove pastry from oven. Reduce oven temperature to 325 degree F.
In a medium mixing bowl toss together mozzarella cheese, cheddar cheese, and 1 tablespoon flour. Sprinkle cheese mixture over bottom of hot pastry shell. In a large mixing bowl stir together eggs, milk, pepperoni, mushrooms or olives, and oregano. Carefully pour egg mixture into pastry shell.
Bake in a 325 degree F oven for 35 to 40 minutes or until a knife inserted near the center comes out clean. Let stand 10 minutes before serving. Meanwhile, heat the pizza sauce in small saucepan over medium heat. Serve quiche with pizza sauce. Makes 6 servings.