Preheat oven to 350 degrees F.
Spray a Dutch oven with vegetable oil cooking spray
Drain 1 can of the peaches. Combine both cans of peaches, including the juice from the undrained can, the blueberries, if using, the baking mix, sugar, and a sprinkling of cinnamon. Place this mixture into the Dutch oven.
To make the topping: Combine the biscuit mix, sugar, butter, and milk in a resealable plastic bag. Drop bits of dough, using your fingers, on top of the peaches. Sprinkle with cinnamon sugar.
Place the Dutch oven into the preheated oven and bake for 45 minutes, until the top is golden brown and crusty.