Grease a 9x9" or 3-quart baking dish with non-stick spray (or line with parchment paper).
In a small pot over medium-low heat, combine the butter, sugar, and vanilla.
Heat until sugar is completely dissolved and butter is melted.
Add the oats and cinnamon and continue to cook over medium heat, stirring constantly, for 5-6 minutes.
Remove from heat and pour half of the mixture into the prepared baking dish.
Press down into the bottom of the dish, making sure it is spread evenly.
In a microwave-safe dish, melt the chocolate for 60 seconds, stirring after 30 seconds. Add the peanut butter and continue to microwave in 30-second incremements until the mixture is smooth and creamy.
Pour ¾ of the chocolate mixture over top of the oatmeal later. Top with the remaining oat mixture followed by the remaining chocolate mixture.
Place in the refrigerator for roughly 4 hours, or until mixture is set.
Remove from fridge and bring to room temperature before cutting into bars and serving.
Recipe by A Taste of Balance at https://atasteofbalance.com/2018/04/10/chocolate-peanut-butter-oat-bars/