Cream butter and sugar and mix in flour and oats and work into a paste. Moisten if necessary with a tsp. of milk. Using a floured board, roll out about 1/4 inch thick and cut into rounds. Put onto a greased baking tray. Bake just above middle in a moderately hot oven at 375 degrees for 20 minutes, until pale brown. Take straight off baking tin on to a wire rack to cool.