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

Bring the mixture to a boil and let it cook for one minute.

Remove the saucepan from heat and stir in the vanilla extract and creamy peanut butter until well combined.

Add the quick-cooking oats to the mixture and mix thoroughly.

Drop rounded teaspoonfuls of the cookie dough onto wax paper.

Allow the cookies to cool completely until they are firm.