1Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9x13-inch baking pan.
2In a bowl, whisk together the flour, baking powder, baking soda, and salt.
3In a large mixing bowl, mash the butter, white sugar, and brown sugar together until smooth and creamy, and beat in the eggs to make a creamy mixture. Gradually beat in the flour mixture, rolled oats, and 1 1/2 cup of butterscotch chips.
4Press the dough into the prepared baking dish, and sprinkle the top with remaining 1/2 cup of butterscotch chips.
5Bake in the preheated oven until the top is golden brown, 30 to 35 minutes. Allow to cool in the pan before cutting into bars and serving.