Preheat the oven to 350℉. For easy removal of the bars, line the pan with parchment paper. Melt the butter and allow it to cool as you prep the rest of your ingredients.
3/4 cups unsalted butter
In a large sized bowl, add in flour, oats, cinnamon, baking soda, baking powder, salt, and brown sugar. Stir to combine.
2 cups all-purpose flour, 1 3/4 cups oats, 1 tsp baking powder, 1/4 tsp baking soda, 1/2 tsp cinnamon, 3/4 cups dark brown sugar
Add in the butter and mix together. A crumbly mixture will form.
3/4 cups unsalted butter
Press about 3/4's of the mixture into the bottom of your pan (I reserved 1 1/2 cups for the top part). You can press this down firmly into your pan using a glass or your hands. Make sure it is evenly distributed and packed down.
Bake the base for 10 minutes at 350F to set the base.
Once baked, remove from oven and scoop peanut butter onto the base. Gently spread it, making an even layer. Since the base is hot, the peanut butter will melt, making it easier to spread.
1 1/2 cups creamy peanut butter
Sprinkle your remaining crumble evenly on top. Add back into the oven for an additional 18-22 minutes or until the crumble is a light golden brown colour. Mine took 20 minutes.
Allow the bars to cool completely. They have to completely cool in order to slice since the peanut butter is melted, or else it will get messy quick!
Once cooled, slice and enjoy! These bars stay good on your counter in an airtight container for 3 days or in the fridge for up to 1 week.