Preheat the oven to 350°F. Spray an 8x8 square baking dish or pan with cooking spray and set it aside.
Mix the rolled oats, pumpkin pie spice, baking powder, and salt in a medium mixing bowl.
In a separate large bowl, combine the pumpkin puree and brown sugar. Add the eggs, vanilla extract, maple syrup, and milk and s9r un9l the eggs are fully mixed in. Fold in the dry ingredients, then pour everything into the greased baking dish and spread it out evenly. Sprinkle the pecans on top, if desired, and bake for 45-50 minutes or un9l the dessert is set and it starts to pull away from the edges of the dish.
Bake for 18-20 minutes until the top is golden and it is firm to the touch.
Let the baked oatmeal cool for 20 minutes, then serve warm with Greek yogurt or whipped cream.
Store in an airtight container in the fridge for up to 3 days.