Preheat the oven to 375° Lightly spray a 8 x 8″ or 9 x 9″ ceramic baking dish with cooking spray; set aside.
Arrange the banana slices in a single layer on the bottom of the ceramic dish. Top with the pears, 1/4 teaspoon of the cinnamon, 2 tablespoon of the maple and cover with foil.
Bake 20 minutes, until the bananas get soft.
Meanwhile,in a medium bowl, combine the oats, half of the walnuts, baking powder, 1/2 teaspoon cinnamon, and salt; stir together.
Ina separate bowl, whisk together the remaining maple syrup, milk, egg, and vanilla extract.
Remove the fruit from the oven, then pour the oat mixture over the baked fruit.
Pour the milk mixture over the oats, making sure to distribute the mixture as evenly as possible over the oats.
Sprinkle the remaining 1/4 teaspoon cinnamon and walnuts over the the top.
Bake the oatmeal for about 35 minutes, or until the top is golden brown and the oatmeal has set. Serve warm from the oven.