Spray a baking pan with nonstick spray.
Add bread cubes to the pan.
In a mixing bowl, whisk together mashed bananas, eggs, milk, cinnamon and vanilla.
Pour the mixture evenly over the bread dish.
Refrigerate for at least 30 minutes, stirring mixture at the 15-minute mark.
Gently stir in the berries.
Preheat oven to 350°F. When preheated, bake the French toast casserole for 40 minutes.
