In a medium bowl, mix together the oats, brown sugar, baking powder, salt, and cinnamon. Set aside.
In another medium bowl, whisk together the milk, eggs, melted butter, and vanilla extract.
Arrange the chopped peaches in the bottom of the crock-pot casserole dish.
Evenly layer the dry oat ingredients on top of the peaches.
Pour the liquid ingredients on top of the oats and use a spatula to make sure the liquid ingredients and the dry ingredients mix together.
Cover and Cook on HIGH for 2 hours or until the center has set.
Cut the baked oatmeal into squares and spoon into bowls. Pour a little milk around the oatmeal and enjoy!