Put butter, sugar, milk and cocoa powder together in to a large saucepan. Bring the mixture to a boil over medium heat. Allow the mixture to boil for 1 minute and 30 seconds. Remove the mixture from the heat. Turn the stove off. Add vanilla extract and peanut butter to the mixture. Stir the mixture until blended well. Add oatmeal to the mixture. Stir the mixture until blended well. Lay wax paper out on to a flat surface. Drop the mixture from tablespoonfuls on to the wax paper. Allow the cookies to cool completely and serve.