Preheat oven to 350 degrees F (175 degrees C). Lightly grease an 8-inch square pan.
In a large bowl, combine brown sugar, oats, flour and butter. Mix until crumbly. Place half of crumb mixture in pan. Spread the apples evenly over crumb mixture. Sprinkle with sugar and cinnamon and top with remaining crumb mixture.
Bake in the preheated oven for 40 to 45 minutes, or until golden brown.