Preheat the oven to 350 degrees F.
Peel, core and slice the apples 1/2 - inch thick.
Toss the apples with the brown sugar, vanilla, cinnamon, flour, nutmeg, and salt.
Spread apples evenly into a 9- x 13- inch baking dish. Dot with bits of butter, if desired.
Spoon cranberry sauce over the apples, and smooth it across the apples as needed.
In a separate bowl mix the oats, flour, sugar and cinnamon. Add the melted butter and stir with a spoon until there are no dry bits of flour/oat mixture left.
Sprinkle the oat mixture over the apples and cranberry sauce.
Bake for 40-60 minutes (depending on how soft you like the apples) and until the topping is golden brown and crunchy. (I baked my crisp for 45 minutes.)
Serve warm with vanilla ice cream or a drizzle of sweetened heavy cream.