Line two baking sheets with parchment paper or set out approximately 29 cupcake liners.

In a 2.5 to 3 quart medium saucepan, combine butter, sugar, cocoa, and milk.

Set over medium heat and cook, stirring frequently, until it reaches a full boil.

Allow mixture to boil 60 seconds without stirring.

Remove from heat and immediately add vanilla, peanut butter, and quick oats.

Stir mixture until well combined, then using a medium (2 Tbsp) cookie scoop or two spoons, drop mixture onto lined baking sheets or into cupcake liners.

Allow to rest at room temperature until set, about 20-30 minutes (refrigerate to speed up).

Store cookies in an airtight container at room temperature.