In a medium saucepan over medium heat, combine the sugar, milk, butter, and cocoa powder. Stir continuously until the mixture is well combined and the butter has melted completely.
Once everything is blended, increase the heat slightly and bring the mixture to a rolling boil. Allow it to boil for exactly one minute without stirring.
After one minute, remove the saucepan from heat. Quickly stir in the peanut butter and vanilla until smooth.
Next, fold in the quick oats, ensuring they are evenly coated with the chocolate mixture.
Using a spoon or cookie scoop, drop heaping spoonfuls of the mixture onto a baking sheet lined with parchment paper.
Allow the cookies to cool at room temperature for at least 30 minutes to an hour.
