Start the oven at 175 degrees Celsius.
Cut the peaches in slices of preferred size.
Butter a pie form and cover the bottom of the form with the peaches.
Sprinkle the sugar evenly over the peaches.
Cut the butter in small pieces and mix it thoroughly together with the oat and the flour until you have big crumbles, and pour it evenly over the peaches.
Place the pie in he middle of the oven for 30 minutes. Take out the pie and let it cool down a while before serving it.