Melt butter and brush some of the butter around the slow cooker.
Using a stand mixer, combine flour, 1-cup sugar, baking powder, and salt. Then, add milk and remaining melted cooled butter, mixing just until dry ingredients are moistened. Pour the batter in the slow cooker and place the frozen peaches on top.
Cook on high for 3 hours with lid on top. Once the cobbler is done, divide and serve cobbler warm with ice cream and whipped cream on top.