Preheat oven to 375 degrees and grease a 9×13 baking pan.
In a large bowl, combine the flour, baking powder, baking soda, and salt. Mix in the oats.
In a separate large bowl, beat the butter, brown sugar, eggs, milk, and vanilla until creamy.
In two batches, add the dry mixture to the wet mixture, beating until just combined. Stir in butterscotch chips and optional nuts.
Spread the batter into the prepared baking dish and bake for 20-25 minutes or until just cooked through. I cover the pan loosely with a piece of foil after about 17 minutes of baking to prevent the top from browning too much.
Cool completely for easier cutting and enjoy!
