In a large mixing bowl, combine peanut butter, rolled oats, maple syrup, cocoa powder, and vanilla extract. Stir until well combined, about 3–5 minutes.

Line an 8x8-inch baking dish with parchment paper. Transfer the mixture into the dish and press down evenly.

In a microwave-safe bowl, melt chocolate chips in 30-second intervals until smooth, stirring in between.

Pour the melted chocolate evenly over the pressed mixture and spread to cover every corner.

Cover with plastic wrap and refrigerate for at least 2 hours to firm up.

Once set, lift the bars out and slice into squares.

Store any leftovers in an airtight container in the refrigerator for up to 2 weeks.