Preheat oven to 350°F (175°C).

Cream together the butter and sugar until light and fluffy.

Stir in the flour and oatmeal until well combined.

Form 1-inch balls of dough.

Place the dough balls onto an ungreased cookie sheet.

Flatten each cookie with a floured fork.

Bake for 10 to 15 minutes, or until golden brown.

Let the cookies cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.

Sprinkle with powdered sugar when cool (optional).