How to Make It
Preheat oven to 375°F. Spread oats in an even layer on a rimmed baking sheet. Bake in preheated oven until golden brown, about 10 minutes. Transfer baking sheet to a wire rack, and cool completely, about 20 minutes.
Beat butter, brown sugar, and granulated sugar with an electric mixer on medium speed until light and fluffy, about 1 minute. Beat in egg. Add vanilla, and beat on low just until incorporated. Whisk together cooled oats, all-purpose flour, baking powder, baking soda, salt, and cinnamon in a bowl. Add to butter mixture in 2 batches, beating on low just until incorporated after each addition. Fold in butterscotch chips and pecans.
Drop dough by tablespoonfuls, leaving 1 inch between the cookies, onto 2 baking sheets lined with parchment paper. Chill in refrigerator 10 minutes.
Bake in preheated oven, switching baking sheets on top and bottom racks halfway through, until cookies are golden brown, 12 to 14 minutes. Cool on baking sheets on wire racks 10 minutes, and transfer to racks to cool completely, about 20 minutes.