Preheat the oven to 350°F. Lightly grease a deep-dish 9-inch pie dish, 9-inch square pan, medium sized cast iron. Set aside.
Peel the peaches (optional, tips below) or don't whichever you prefer! Slice the peaches, add them to the baking dish. Add the vanilla, lemon, sugar and flour. Mix well.
Whisk the oats, brown sugar, chopped pecans, flour, cinnamon, nutmeg and salt together in a medium bowl. Cut in the butter using a knife and mix the crumble with your hands or forks until the mixture is crumbly.
Lightly grease a deep-dish 9-inch pie dish, 9-inch square pan, a medium sized cast iron skillet with oil or butter. Add in the sugared peaches. Top with the crumble, lightly mix in some of the topping so it's throughout the dish.
Bake for 40–50 minutes until the topping is golden brown and the peach juices are bubbling around the edges. Remove from the oven, and allow to cool for a few minutes before serving warm. Optional to add ice cream.