Apple Pie Filling:
Core, peel and cut apples in chunks. Toss with lemon juice to coat to prevent from browning too much, set aside.
Stir together sugars, cornstarch, cinnamon, and nutmeg in a large saucepan. Whisk in water until everything has dissolved. Bring the mixture to a boil over medium-high heat. Reduce the heat slightly and simmer for 2 minutes. Add the apples and increase the heat to medium-high and bring to a boil again. Reduce the heat to low and simmer, stirring occasionally, for 10-12 minutes until the apples softens and the sauce thickens. Remove the pan from the heat and let the mixture cool to room temperature.
To Make the Oatmeal Crust:
Melt butter over medium heat, then stir in brown sugar until sugar is dissolved.
Add vanilla, cinnamon and pecans and stir until combined.
Turn heat to low and add quick cooking oats. Cook on low for about 2 minutes, or until ingredients are well combined.
Reserve about 1/3- ½ cup of the oat-pecan mixture for sprinkling on top for decoration.
Grease the bottom of 9 x 13 inches dish and press remaining mixture into the bottom of the pan. Place in the fridge to firm.
Vanilla Cream Cheese Layer:
