Preheat oven to 350F degrees. Peel and slice sweet potatoes and apples and place in bowl. Set aside until ready for use.
Sparingly grease 8X8 glass baking dish with some of the butter and sprinkle some of the brown sugar in the bottom. Add flour, cinnamon, and brown sugar to the sliced sweet potatoes and apples. Dot with remaining butter and bake for 45 minutes.