• In a medium bowl, whisk together the gluten-free all-purpose flour, pumpkin pie spices, baking powder, baking soda, and salt. Set aside.
• In the bowl of a stand mixer fitted with the paddle attachment or a hand mixer, beat together the softened butter and sugars on medium-high speed until light and fluffy (about 3 to 5 minutes). Add the pumpkin puree, egg, and vanilla extract. Reduce the speed to low, gradually add the dry ingredients, and mix until combined. Don’t overmix.
• Finally, fold in the oats by hand with a rubber spatula. Let the dough rest covered in the refrigerator for 1 hour.
• Preheat the oven to 350°F (180°C). Line 2 baking sheets with parchment paper or a silicone mat.
• Let the dough soften at room temperature for 5 to minutes, scoop balls, and place on the prepared baking sheets, leaving space between them. Bake for 15 minutes or until golden brown. Let cool for 5 minutes before removing to a wire rack to cool completely.

For the icing:

• In a small bowl, mix the powdered sugar and milk. If the glaze is too thick, add more milk, 1 teaspoon at a time. If it’s too runny, add more powdered sugar. When the cookies are completely cold, drizzle with the glaze and allow to set.