1. Preheat the oven to 375F. 2. Lightly grease a 2-quart baking dish. In a medium bowl, mix the oats, half of the walnuts, baking powder, cinnamon, and salt. Stir to combine. In a liquid measuring cup, combine the syrup, milk, egg, butter, and vanilla. 3. Spread the sliced bananas in a single layer over the bottom of the baking dish. Top with half of the berries. Sprinkle the dry oat mixture over the fruit in an even layer. Pour the liquid ingredients evenly over the oats. 4. Sprinkle the remaining nuts and berries over the top. Bake for 35-40 minutes, until the top is browned and the oats have set. Let cool 10 minutes before serving.