In a medium saucepan, combine sugar, milk, butter, and cocoa. Bring to a boil, and cook for 1 1/2 minutes. Remove from heat, and stir in peanut butter, oats, and vanilla. Drop by teaspoonfuls onto wax paper. Let cool until hardened.
**IMPORTANT** do not let the butter and sugar mixture boil beyond the 1.5 minutes or else your cookies will not become hard they will remain gooey and they aren't fun to eat that way...Happy Baking ;)