In a large mixing bowl, combine rolled oats, creamy peanut butter, honey (or maple syrup), and unsweetened cocoa powder. Mix thoroughly until ingredients are well incorporated.

Line an 8x8-inch baking dish with parchment paper. Scoop the mixture into the prepared dish and press down firmly to form an even layer.

In a microwave-safe bowl, add chocolate chips for topping. Microwave in 30-second intervals until fully melted and smooth, then drizzle over the pressed mixture.

Place the baking dish in the refrigerator and let it chill for at least 30 minutes until the chocolate hardens.

Once set, lift the mixture out using the parchment paper and cut into squares or rectangles to serve.