For each apple you need:
1 1/2 tablespoons dark brown sugar
1 1/2 tablespoons oats
1/4 teaspoon cinnamon
1 1/2 tablespoons unsalted butter
Wash apples and remove core so you have a good size "well" in each and place in baking dish (or individual dishes, I love the Le Creuset petite cocottes).
Mix together sugar, oats and cinnamon, pack the mixture into the apples and top each with a pat of butter.
Bake loosely covered in foil for 30 minutes at 350 (I use the toaster oven if I'm only making a couple). Uncover and bake for another 5-10 minutes, until top is a little golden brown.