Heat oven to 350°F. Line two baking sheets with parchment paper.
Whisk flour, baking soda, salt, and cinnamon in a medium bowl.
Cream softened butter, brown sugar, and granulated sugar until fluffy, about 2 minutes.
Beat in the eggs and vanilla until smooth and well combined.
Mix in the dry ingredients on low speed just until no dry spots remain.
Fold in oats and butterscotch chips until evenly distributed.
Scoop rounded tablespoons of dough onto prepared sheets, spacing about 2 inches apart.
Bake 10–12 minutes, until edges are set and centers look slightly soft.
Cool cookies on the sheet for 5 minutes, then move to a rack to finish cooling.