Preheat the oven to 375 degrees F (190 degrees C).

In a saucepan, combine the raspberries, cherries and white sugar. Cook over medium heat until soft. Remove from the heat and set aside.

In a separate bowl, mix together the oats, brown sugar, cinnamon, and melted butter.

Use a slotted spoon to spoon the fruit into the pie crust, avoiding adding too much juice. Sprinkle the oat mixture over the top.