Combine wet ingredients: In a medium saucepan, combine butter, sugar, milk, and cocoa. Bring to a rolling boil for 1 minute and 15 seconds.
Mix dry ingredients: While the mixture is boiling, measure out peanut butter, oats, and vanilla.
Combine: Remove the saucepan from heat. Stir in peanut butter, oats, and vanilla until well combined.
Shape: Drop by tablespoons onto wax paper-lined baking sheets.
Cool: Let cool for 30 minutes or until set.
