Preheat your oven to 350 degrees. Line a baking sheet with parchment paper.
In a medium bowl add the flour, baking powder, baking soda and salt and whisk together.
In a large bowl add the softened butter, granulated sugar and brown sugar and using a hand mixer beat on medium until creamy.
Add in the egg and vanilla and mix.
Add in the dry ingredients and mix just until combined.
Mix in the old fashioned oats just until combined.
Using a wooden spoon or spatula fold in the butterscotch chips.
Scoop 2 tablespoons of cookie dough and gently roll into balls or use a cookie scoop. Place a few extra butterscotch chips on top.
Bake for 8-10 minutes
Notes
Make sure not to overbake, these cookies are supposed to be chewy and they will become crunchy if overbaked.I always recommend doing a two-cookie test run with your oven to properly adjust the time if needed.Make sure you butter is at room temperature and not melted or else your cookies will spread all over the place.Place the cookie sheet in the center of your oven for the best even cooking.You don't have to chill the dough but you certainly can if you prefer. You can store the dough in the refrigerator for up to 3 days.I always use light colored cookie sheets lined with parchment paper so they don't burn.