Preheat oven to 350 degrees. Line baking sheets with parchment paper or spray with non-stick cooking spray.

With an electric mixer, cream butter and sugars until smooth and fluffy. Add the egg, egg yolk and vanilla, beating well after each addition.

In a medium bowl, stir together the flour, oats, baking powder, baking soda and salt. Add to the creamed mixture and mix well. Stir in chocolate chips.

Drop dough by rounded tablespoons onto prepared baking sheets. Bake for 10-12 minutes, or until cookies are light golden brown with slightly darker edges. Do not over bake.

Let cookies sit on baking sheets for 2-3 minutes before transferring to a wire rack to cool completely.