In a large bowl, combine sliced peaches, lemon juice, lemon zest, vanilla extract, granulated sugar, and flour. Gently toss until fruit is well coated. Allow the fruit mixture to sit while you prepare the crumble topping.
For the crumble topping, take a large bowl and combine the flour, oatmeal, brown sugar, granulated sugar, salt, and cinnamon. Stir together with a whisk. Mix in the butter with your hands until it forms a coarse mixture and there are big crumbles. (I didn't like using my hands so I used a pastry blender).
Place the fruit mixture in a 10 inch skillet or glass baking dish. Sprinkle the crumble mixture evenly over the fruit. Bake for 40 to 45 minutes, or until the top is browned and crisp and the juices are bubbling. Serve warm with vanilla ice cream.