Pre-heat the oven to 350° F. Line an 8×8 pan with parchment paper.
In a large mixing bowl, using an electric mixer, combine the butter, brown sugar, and granulated sugar. Add the flour, egg, peanut butter, baking soda, vanilla, and salt to the mixing bowl. Mix until well combined. Stir in the oatmeal and chocolate chips.
Spread evenly in your pan (top with additional chocolate chips as desired for looks – and, chocolate!). Bake for 16-20 minutes until edges begin to brown. It’s ok if the middle seems a bit underdone – it’s like cookies, you don’t want them over baked; it will continue to set up as it cools.