In a medium saucepan over medium high heat, combine sugar, butter, and milk.
Bring to a rapid boil and boil for 2 minutes and 30 seconds (SET A TIMER!) stirring continuously.*
Remove from heat and stir in the vanilla and the peanut butter. Stir in the oats until well blended then immediately drop by tablespoons onto waxed paper. Let cool until set. This takes a while, so hands-off for about 30 minutes! :)
Notes
If you boil these cookies for exactly 2 minutes and 30 seconds, they should turn out wonderfully, however, please note that this type of no-bake cookie is not an exact science and there are many atmospheric factors that could vary your results.For instance, the last time I made these cookies it was a humid, rainy day and they took much longer to set. I've made these cookies MANY TIMES, and there are those fluke days when they turn out too dry or too moist, but generally, I have excellent results.