Preheat your oven to 350°F (175°C). In a large bowl, combine sliced peaches with sugar, cornstarch, cinnamon, nutmeg, lemon juice, vanilla, and salt. Gently toss until everything is well coated.

Pour the peach mixture into your baking dish and spread it out evenly.

In another bowl, mix flour, brown sugar, cinnamon, salt, and oats. Add the cold butter and cut it in using a pastry cutter or fork until the mixture resembles coarse crumbs.

This texture is important. You want little pockets of butter that will melt and crisp in the oven.

Sprinkle the crumble topping evenly over the peaches. Don’t press it down too hard—let it sit naturally.

Bake for 45–50 minutes, or until the top is golden brown and the peach filling is bubbling around the edges.

Let it cool slightly before serving. The filling thickens as it rests.