Arrange sliced peaches in 10 inch square baking dish, Pour lemon juice on peaches. Spread brown sugar over peaches. Then sprinkle on cinnamon. In mixing bowl combine flour, sugar, baking powder,and salt. Add milk and beat til smooth, batter will be very thin. Pour batter over peaches. Drizzle melted margarine over batter. Bake for 35 minutes in a 350 degree oven.