In a large mixing bowl, stir together flour, sugar, oats, and pecans.
One tablespoon at a time, mix in softened butter. It's helpful to use a fork or your clean hands to mix everything together. You want the butter to coat the rest of the ingredients. It is thoroughly mixed when the mixture is in pea sized "crumbles"
Sprinkle crumble over fruit mixture, covering it completely.
Bake at 400 degrees for 35-40 minutes. Place a cookie sheet under your pan to catch drips in case the crumble boils over. You know it's done when you stab an apple and it's soft all the way through. If your top starts to get too dark before the apples are done, cover with aluminum foil
Allow to cool completely and enjoy!