I stole this recipe shamelessly from Smitten Kitchen, with only a couple changes.
* 1 cup (2 sticks) butter, softened
* 1-1/3 cup light brown sugar, packed
* 2 eggs
* 1 teaspoon vanilla extract
* 1-1/2 cup all-purpose flour
* 1 teaspoon baking soda
* 1 teaspoon ground cinnamon
* 3/4 teaspoon salt
* 1 1/2 cups rolled oats
* 3/4 cup raisins (I recommend Newman's Own organic)
Preheat oven to 350°F. (Note: I usually preheat my oven to 25 degrees lower than what recipes say, because it runs about 10 degrees hot and also I use nonstick bakeware. So I actually baked these at 325. I also didn't use parchment paper and my cookies were fine.)
In a large bowl, cream together the butter, brown sugar, egg and vanilla until smooth. In a separate bowl, whisk the flour, baking soda, cinnamon and salt together. Stir this into the butter/sugar mixture. Stir in the oats and raisins.
Cover the dough and chill it in the fridge for at least one hour. Using cold dough helps the cookies bake up thick and chewy.
Roll dough into balls of about 1.5 tablespoons each. I use a medium OXO cookie scoop and put 9 cookies on each cookie sheet. Bake for 10-15 minutes taking them out when golden at the edges but still a little undercooked-looking on top (mine took about 14 minutes). Let the cookies sit on the hot baking sheet for five minutes before transferring them to a rack to cool.
Yields about 3 dozen cookies.