Line a baking sheet or counter with wax paper.

Combine sugar, milk, butter, and cocoa in a medium saucepan.

Bring to a rolling boil over medium heat; boil exactly 1 minute.

Immediately remove from heat; stir in peanut butter and vanilla until smooth.

Fold in quick oats until fully coated.

Drop spoonfuls onto wax paper; stand at room temperature until firm.