Line an 8x8 inch baking pan with parchment paper.

In a medium saucepan, combine butter, sugar, milk, and cocoa powder.

Bring the mixture to a rolling boil over medium-high heat.

Boil for exactly 60 seconds, then remove the saucepan from the heat source immediately.

Stir in the creamy peanut butter and vanilla extract until the mixture is smooth.

Fold in the quick-cooking oats until they are thoroughly and evenly coated.

Pour the mixture into the prepared 8x8 inch pan and spread into an even layer using a spatula.

Allow the pan to cool at room temperature for 15 minutes.

Transfer to a refrigerator and chill for at least 1 hour until the bars are firm.

Slice into 16 equal squares for serving.