Add the sugar, butter, salt, and milk into a 5- quart sauce pot over medium heat. Stirring frequently, bring the mixture to a boil. Boil rapidly for 2 minutes and then remove the pot from the heat.
Stir in the vanilla and peanut butter until smooth. Add in the oats and stir until combined.
Line a large baking sheet with parchment paper or waxed paper. Using a 1 ½- tablespoon cookie scoop portion out the mixture onto the pan. Flatten the cookies slightly and allow them to cool completely, about 30 minutes, before serving or storing.
