Preheat the oven to 350 degrees Fahrenheit and line two large baking sheets with parchment paper or spray with cooking spray.
Cream together the butter, brown sugar and white sugar in a large mixing bowl with a hand or stand mixer until light and fluffy.
Beat in the egg until combined. The mixture may not be completely smooth.
Mix in the flour and baking soda, stirring just until combined.
Fold in the old fashioned oats and butterscotch chips until evenly distributed.
Use a 1 ½ Tablespoon cookie scoop to drop cookie rounds onto the prepared baking sheets.
Bake for 9-13 minutes or until golden brown on the edges and set in the middle.
Cool completely before serving.
Notes
Store leftover cookies in an airtight container at room temperature for up to a week. Ensure the cookie are fully cooled before storing. You can also store the cookies in a freezer bag or airtight container in the freezer for up to 3 months.