In the bowl of a stand mixer, add butter and both sugars. Beat with paddle attachment at medium-high, until butter mixture is fluffy and light. Add eggs and vanilla, and beat to combine.
In a separate bowl, whisk together the flour, baking soda, ground cinnamon, and salt. Gradually add flour mixture to the butter mixture, on medium-low speed just until dry ingredients are mixed in; don't over beat.
Stir in the rolled oats and butterscotch chips by hand.
Chill dough in fridge about 30 minutes to an hour.
Meanwhile, preheat oven to 350F and line baking sheets with parchment.
Form walnut-sized balls and place balls 2 inches apart on cookies sheets.
Bake about 8 minutes. It will seem under baked, but firms up when cool.
Let cool on baking sheet about 5 minutes. Transfer to wire rack to cool completely.