Preheat oven to 375 degrees F.

Peel and slice apples, throw away core.

Mix apples in 9 x 9 pan with ¼ cup brown sugar and ¼ cup sugar (rest is for crumble). Add half the cinnamon.

In another bowl—add flour, oats, butter, rest of the sugar, and cinnamon.

Mix crumble ingredients with your hands. Smashing the butter into the batter and squeezing. Keep doing till well combined.

Add crumble to the top of the apple mix.

Bake for 15 minutes at 375 F then lower temperature to 350 F and bake 20 more minutes.

Serve with vanilla ice cream or whipped cream.