Preheat the oven to 350°F. Line baking sheets with parchment and set aside.

By hand or in the bowl of a stand mixer fitted with a paddle, beat the butter and brown sugar until light. Add the egg and vanilla, and beat until well combined.

In a medium bowl, combine the flour, baking soda, baking powder and salt. With the mixer set on low, or by hand, stir the flour into the butter mixture. Mix until smooth. Stir in the oats.

Roll or use a cookie scoop to form dough into 1-tablespoon rounds. Place 2 inches apart on the prepared sheet. The cookies will flatten and spread, so give them room.

Bake 10 to 12 minutes or until the cookies are light brown. Let cool for a couple of minutes and then transfer to a wire rack to cool.