Spray a 9 by 13-inch baking pan with cooking spray. Slice the baguette into 1/2-inch slices and arrange the slices in a single layer in the baking pan. Whisk together the eggs, egg whites, milk and vanilla. Pour the egg mixture over the bread in the pan. In a medium bowl, toss peaches with the lemon juice and 1 tablespoon of the brown sugar. Scatter the peach slices evenly on top of the bread. Combine the remaining brown sugar and cinnamon and sprinkle over the top. Cover and refrigerate overnight.
Preheat the oven to 350 degrees F. Uncover and bake for 40 minutes.
Serving suggestion: Top with a dollop of vanilla yogurt, a drizzle of maple syrup and a side of Canadian bacon.