In a large bowl, whisk together the flour, baking soda, baking powder, salt, and spices. Stir in the oats; set aside.
In the bowl of a stand mixer fitted with a paddle attachment, cream the butter until smooth. Add the brown sugar and white sugar and beat until fluffy. Add the pumpkin, egg yolk, and vanilla, and beat until smooth. Dump in the flour mixture, mixing until just combined.
Preheat the oven to 350ºF and line a baking sheet with parchment paper. Using a cookie scoop or two spoons, scoop cookie dough onto prepared baking sheets. Using grease hands, roll dough into 1-inch balls, about 2 Tablespoons of dough per cookie. Place dough balls onto prepared baking sheet, then use the bottom of a measuring cup greased with cooking spray to flatten to about 1/2 of an inch.
Bake for 8-10 minutes, or until lightly browned around the edges. Allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.