Butter the inside of the crock or spray with cooking spray.
Stir together brown sugar, oats, flour and cinnamon.
Cut the butter into the dry ingredients with a pastry blender or fork until the mixture is crumbly.
Put the drained peaches in the crock and stir 1/2 the crumbs into the fruit.
Top with the rest of the crumbs.
Cook on low 3-4 hours.
If you want to really crisp it up, pop the crock under the broiler for a minute before serving. We skipped that step and it was still delicious and a little bit crispy around the edges.