Line two baking sheets with parchment or wax paper. Set aside.
Combine the sugar, butter, milk and cocoa powder in a saucepan over medium-heat. Bring to a boil (not simmer). Once it reaches a boil, cook for an additional 1 1/2 minutes and then immediately remove from heat.
Stir in the peanut butter and vanilla. Add in the oats and stir until well coated.
Drop batter by the spoonful onto the lined pan. Let cool until set. Store in an airtight container at room temperature.
Line your baking sheets with parchment or wax paper so the cookies don't stick.
Do not use old fashioned oats, quick oats are a must for this recipe.
Before removing the pan from the burner, make sure the mixture is boiling (not simmering).
In order to speed up the setting process, place cookies in refrigerator to harden faster.
To store: Store at room temperature for 3-4 days or in the fridge for 5-7 days.
To freeze: Let set completely, then add to freezer bag or airtight container. Store in freezer for 2-3 months.