Melt the butter.
Combine melted butter, brown sugar, and flour in a small bowl and stir until mixture looks like small crumbs.
If using fresh peaches, wash them thoroughly and slice them, leaving the skins on. If using canned peaches, drain them now.
Add the peaches to a 9x9 inch baking dish.
Sprinkle the topping over the prepared peaches, and bake the mixture for approximately 30 minutes at 350 degrees.
Serve with vanilla ice cream.