In a bowl combine 3/4 cup of melted butter, 2 cups of flour, 1 cup of brown sugar and 1/2 cup rolled oats.
Combine all of the above --Reserve 1 Cup of the mixture--press the rest into a 9x13 pan that you've sprayed with cooking spray.
6 cups of apples peeled and sliced. Place on the crust
In a sauce pan, combine 1 cup of sugar, 1 cup of water, 1 t vanilla, 1/2 t cinnamon and 1/4 cup of flour. Cook over medium heat and stir constantly until it comes to a boil. Pour over the apples.
Spread reserved crust over the apples and bake for 45 minutes.
**When I make the recipe, I double crust and apple portion and make only one batch of sauce...for me, it's sweet enough to cover two pans. If you have a stronger sweet tooth, you may want to try the recipe as is the first time through.