Eating Blueberry Peach Crisp for dessert is just like eating the most delicious oatmeal cookie you've ever had with the added benefit of warm summer fruit!
Place peaches and blueberries in a baking dish (10x10" square or 9x11" oval, 9x13" rectangle can also be used). Mix sugar and cornstarch together and sprinkle over fruit. Add vanilla and lemon juice, stir to combine.
Mix oats, flour, and brown sugar together in a small bowl. Add butter and mix to combine until mixture is crumbly. Spread over fruit mixture.
Bake in preheated oven for 1 hour, until fruit mixture is thick and the topping is golden brown.