Add the oats, peanut butter, chocolate chips, and vanilla to a medium mixing bowl; set aside.

Line 2 rimmed baking sheets with waxed paper and set aside.

Combine the butter, milk, and sugar in a small, heavy saucepan set over medium-high heat.

Boil for 1 minute.

Pour the hot milk mixture into the oat mixture and stir well.

Drop spoonfuls onto the waxed paper and cool, refrigerated, until the cookies set.

If youre in a hurry, you can pop the cookies in the freezer to set faster.

Remove from the waxed paper and serve.