Preheat the oven to 350°F (177°C). Grease a 9-inch square baking pan, 11×7-inch baking pan, or similar-size baking dish (that holds about 2.5 quarts) with nonstick spray. Set aside.

In a large bowl, whisk together the milk, eggs, maple syrup, melted butter, pumpkin, and vanilla until combined. Stir in the oats, baking powder, pumpkin pie spice, cinnamon, salt, and pecans. Pour into the prepared baking pan.

Bake for 38–45 minutes or until the center appears almost set. Cool for 5 minutes before slicing and serving.

In a medium bowl, whisk together the sifted confectioners’ sugar, maple syrup, and milk until smooth. Drizzle over the top of the warm baked oatmeal (either the entire casserole or plated portions) and serve.

Tightly cover leftover pumpkin baked oatmeal and store in the refrigerator for up to 1 week.