Oatmeal cookies with just oats, sugar, and butter?

I use this recipe from Swedish Food
3 cups quick oats
2/3 cup butter
1/2 cup sugar, mix well, Make into balls and flatten with a fork. Bake at 325 for 8 min till light brown. Makes 50

A friend of mine made these for me when I was visiting her in England. I've made them many times since I returned and everyone who has tasted them loves them. I use Turbinado sugar, which I believe is the same as Demerara sugar. http://www.deliaonline.com/recipes/main-ingredient/oats/oat-crunch-biscuits.html

You could make something like this: http://www.remedialeating.com/2012/05/some-truths.html

Oats sugar and butter makes great oatmeal but not cookies.

Not quite that simple (I add a small amount of flour, salt and vanilla) but I make cookies similar to this all the time. You can add nuts, spices or whatever (recently made a batch with chopped crystallized ginger) - but the essential cookie is very elemental, close to what you describe: http://www.food52.com/recipes/16176_dans_second_favorite_cookie_aka_oatmeal_brown_sugar_crisps