Preheat the oven to 350°F. Lightly spray a 9x13 inch baking pan with cooking spray and set aside.
In a large bowl, mix together all of the filling ingredients. Pour into the prepared baking pan and spread evenly on the bottom.
In a food processor, pulse all of the "topping" ingredients except for the oats until the butter looks like coarse meal. Mix in the oats and spread evenly on top of the fruit mixture.
Bake in the oven for around 40-45 minutes. Allow to cool for around 5 minutes before serving.
Notes
Using rolled oats gives the best texture, but you can use quick oats.