Preheat oven to 350°. Grease a 9 x 13 casserole pan preferably with butter.
In the bowl of a stand mixer cream together butter, granulated sugar, brown sugar, and peanut butter. Mix in vanilla and egg.
In a medium bowl mix together flour, baking soda, salt, and oatmeal. Add flour mixture to peanut butter mixture and mix until combined.
Spread batter into greased pan and sprinkle butterscotch chips over top. Bake at 350° for about 20 to 25 minutes just until edges are brown.
While the batter is baking combine all ingredients for the glaze into a bowl of a stand mixer and beat until smooth. Pour and spread the waves over the top of the bars while they are still warm. Let cool completely before cutting.