Place butter in microwave-safe bowl and microwave for 20 seconds. The butter should be partially melted. Stir it a few times and set aside to cool.
In a large mixing bowl, whisk together oats, flour, baking powder, soda, pumpkin pie spice and salt.
In another mixing bowl, whisk melted butter with both sugars. Whisk for 15 to 20 seconds. Add vanilla and egg yolk and whisk until the egg is incorporated. Add pumpkin and whisk until incorporated.
Add dry ingredients to wet ingredients and stir in with a wooden spoon. Stir in chocolate chips.
Cover the bowl with dough with saran wrap and chill for 30 minutes.
Preheat oven to 350° F. Line a baking sheet with parchment paper.
Scoop dough with 1 ½ tablespoon size cookie scoop and place onto prepared baking sheet.
Bake cookies for 9 to 11 minutes. Remove from oven and cool on sheet for 5 minutes. Then transfer onto a cooling rack. Place 3 to 4 chocolate chips on top of each cookie to make them pretty, if desired.
Notes
To jazz up these Pumpkin Oatmeal Cookies, I added semi-sweet chocolate chips. Chopped chocolate bar would be perfect here too. You can also add nuts, like pecans or walnuts if you like. Butterscotch or white chocolate chips will be great in this recipe as well.
Please note, that the nutrition value can vary depending on what product you use. The information below is an estimate. Always use a calorie counter you are familiar with.