Preheat oven to 350°F (175°C) and grease a muffin tin.
Chop fresh peaches and set aside.
In a bowl, whisk together flour, sugar, baking powder, and salt.
In another bowl, mix melted butter, eggs, milk, and vanilla; combine with dry ingredients until just mixed.
Gently fold in chopped peaches.
Prepare crumble by mixing brown sugar, oats, cinnamon, and cold butter until crumbly.
Fill muffin cups two-thirds full with batter; top generously with crumble.
Bake for 18-22 minutes or until golden brown; cool slightly before serving.
