With a stand mixer or electric hand mixer, cream together the butter and peanut butter.
Add the sugars and mix well.
Add vanilla + eggs and mix to combine.
Next, add the dry ingredients. Combine the flour, oats, and baking powder in a small bowl, and then add to the large bowl. Mix until just combined then add the chocolate chips.
Scoop the batter into the pan and push it around to even it out. Use a wet spoon (keep re-wetting it) to smooth out the top.
Bake for 20-25 minutes.
Let it cool for a few minutes in the pan, then use the parchment to help lift it out onto a cooling rack to let it cool completely. This makes it easier to cut although it is super tasty when it's still warm, so you could dig in right away if you want to. I cut it into 24 squares.