Step 1

Preheat oven to 400°F. Line a rimmed baking sheet with foil or parchment paper. Rub squash halves evenly with oil; arrange, cut-side down, on the prepared baking sheet. Bake until very tender, about 45 minutes. Let cool for about 20 minutes. Reduce oven temperature to 350°F.

Step 2

While the squash cools, lightly coat a 9-inch-square baking dish with cooking spray; set aside. Combine oats, pecans, 1/4 cup brown sugar and 2 tablespoons melted butter in a medium bowl; set aside.

Step 3

Scoop the squash flesh into a large bowl; discard shells. Mash the squash with a fork until smooth. Stir in milk, eggs, cornstarch, salt, cinnamon and the remaining 1/2 cup brown sugar and 2 tablespoons melted butter. Spoon the mixture into the prepared baking dish; sprinkle evenly with the oat mixture. Bake until golden and set, about 35 minutes. Let stand for 15 minutes before serving.