Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper or silicone baking mats to prevent the cookies from sticking and to ensure even browning.
In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar together until the mixture is light and fluffy. This should take about 2 to 3 minutes using an electric mixer.
Add the egg and vanilla extract to the butter mixture and beat well. Stir in the pumpkin puree until fully combined. Don’t worry if the mixture looks slightly curdled at this stage; it will come together once the dry ingredients are added.
In a separate medium bowl, whisk together the flour, baking soda, cinnamon, pumpkin pie spice, and salt. Gradually add this dry mixture to the wet ingredients, mixing on low speed until just combined.
Using a spatula, gently fold in the rolled oats and the chocolate chips. Ensure they are evenly distributed throughout the dough without overworking the batter.
Scoop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart. Bake for 10 to 12 minutes, or until the edges are lightly golden. Let them cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.