In a bowl, beat eggs, milk, vanilla and baking powder until smooth. Pour into a large shallow baking dish. Add bread slices, turning once to coat. Cover and chill for 8 hours or overnight. combine blueberries, sugar, melted butter, cornstarch and cinnamon.
Pour into a greased 13x9 inch baking pan.
Bake, uncovered, at 400 F for 30-35 minutes or until toast is golden brown and blueberries are bubbly