Grease a 9 x 13 inch baking pan with cooking spray. Slice French bread into 1-inch chunks and spread half of them in the pan. Sprinkle half the berries on top. Repeat with the remaining half of bread chunks and berries.
In a medium bowl, whisk together milk, eggs, cinnamon, vanilla, and brown sugar until smooth. Pour over bread, pressing down the top with a spatula to help bread soak up the milk mixture.
Cover and refrigerate at least 3 hours (overnight is preferable). Bake in a 350 degree oven for 50-55 minutes. Serve with maple syrup.