Spray or lightly butter the inside of a square 8-inch baking dish.
Combine oats, baking powder, cinnamon, and salt.
In separate bowl, whisk together maple syrup, milk, egg, butter, and vanilla.
Layer sliced bananas across the bottom of baking dish and cover with a layer of about 1 cup of berries on top of the bananas.
Combine dry and wet ingredients, stir and mix well. Pour oat mixture on top of fruit.
Sprinkle mixed nuts over the top.
Bake for 35 to 45 minutes uncovered. Top will brown and oat mixture will set/firm.
Remove from oven. Can serve hot. To store let cool, then refrigerate.
Reheat small portion in microwave or in oven. Serve in bowl with milk poured over the top.
Start with bananas that have a little green in them. The firm banana is easier to cut, doesn’t get mushy, and has a baked apple texture.
Layer the fruit on the bottom. I tried many times to put some fruit on top and it always sinks to the bottom.
Strawberries are a no go! Trust me. They get very soggy, taste funny after a day, and don’t reheat well at all! Frozen tropical fruits like pineapple/mango mixtures work well if you leave out the cinnamon.