Line a square baking tin with baking paper and preheat the oven to Gas mark 4 or 180 degrees.
Mix together porridge oats, butter, flour, sugar and maple syrup in a large bowl until it forms an oat-based dough.
Place approximately two-thirds of the mixture in the baking tin and flatten. Bake for 10 minutes.
Spread out the raspberries and blueberries on top of the base. Crumble the remaining third of the oat-based dough on top and sprinkle on top.
Optional: To soften the blueberries prior to baking, warm through in a saucepan with a little water to make a coulis before adding to the base.
Bake in the oven for 20 minutes or until golden. Serve immediately as dessert, or leave to cool to slice into snack bars.