In a large bowl, stir together all the ingredients except ¼ cup chopped pecans, the Cool Whip, and the optional maple syrup.
2 cups old fashioned rolled oats, 1 teaspoon baking powder, 1½ teaspoons pumpkin pie spice, ½ teaspoon coarse sea salt, 1 cup milk, 1 cup pumpkin puree, ¼ cup maple syrup, 2 tablespoons brown sugar, 1 large egg, 1 teaspoon pure vanilla extract, ½ cup chopped pecans