01 - Preheat the oven to 350°F (175°C). Grease a 9x9-inch baking dish thoroughly with butter or non-stick spray.
02 - In a large mixing bowl, thoroughly mix together the rolled oats, chopped nuts, baking powder, ground cinnamon, ground nutmeg, and salt.
03 - In a separate bowl, whisk together the milk, eggs, melted unsalted butter, maple syrup, and vanilla extract until smooth.
04 - Pour the liquid mixture over the oat mixture and stir until well combined. Gently fold in diced apples and dried fruit.
05 - Pour the combined mixture into the prepared baking dish and spread evenly.
06 - Place the dish in the oven and bake for 35 minutes, or until the top is golden brown and the oatmeal is set in the center.
07 - Remove the dish from the oven and allow to cool for at least 5 minutes before serving. Serve warm, optionally topped with extra milk or yogurt.