Combine the oats, peanut butter, maple syrup, and coconut oil in a mixing bowl and mix thoroughly until fully blended, resembling a thick batter.

Add the cocoa powder to the mixture and mix until completely uniform in texture.

Line an 8x8-inch baking dish with parchment paper and transfer the mixture, pressing it down evenly.

Melt the dark chocolate chips in a microwave-safe bowl in 30-second intervals until fully melted.

Pour the melted chocolate over the oat mixture and spread evenly across the surface.

Refrigerate for at least two hours until set and chocolate is hardened.

Remove from the dish, cut into squares or rectangles, and serve.