This recipe started out as Alton Brown’s Oatiest Oatmeal Cookies Ever recipe on the Food Network web site (note: There are actually two different versions of the recipe available online; general consensus seems to be that the one I’ve linked to is the correct recipe). I then tweaked things up a bit to my own tastes.

Note: This recipe is gluten-free.

Ingredients

16 ounces (about 4⅔ cups) oats (not quick oats)
1 teaspoon baking powder
1 teaspoon ground cinnamon
¼ teaspoon salt
10 ounces (about 1¼ cup) butter (softened)
6 ounces (about 1 cup lightly packed) brown sugar
3 ½ ounces (about ½ cup) granulated sugar
1 large egg
2 teaspoons vanilla extract
6 ounces (about 1¼ cup) raisins or dried cranberries (or a mix of both)

Directions

Preheat the oven to 375 degrees.

Spread the oats on a large baking sheet (do not grease the baking sheet). Bake until the oats are lightly toasted. This should take about 20 minutes. I usually stir the oats around a bit half-way through this process to help make sure they get more evenly toasted. When toasted, let the oats cool  for 2-3 minutes.

Take approximately half of the toasted oats and grind them in a food processor until they resemble a coarse flour (2-3 minutes).

Add the baking powder, cinnamon, and salt to the ground oat mixture and pulse the food processor a few times to mix well.

Combine the sugars and butter in a bowl and beat until well mixed (you can mix by hand, but I prefer to use a mixer). Throughout the mixing process here and below, scrape down the sides of the bowl as necessary to make sure that the mixture is completely integrated.

A note on the butter in this recipe: For most cookie recipes, to ensure proper batter consistency your butter should be soft and roughly room temperature. This often stymies me, because it means I have to plan ahead and leave some butter out to soften. If I instead try to soften the butter in my microwave, I often end up with partially melted butter, and the batter ends up too soupy. Because we simply pour the batter for this recipe into a pan, it doesn’t matter if the batter is soupier. If you don’t have soft butter, go ahead and just throw it in the microwave. Even if it’s mostly melted, this recipe will still come out just fine.

Add the egg and vanilla. Mix on low speed until combined.

Slowly add the ground oat mixture, mixing on low speed until completely combined.

Add the remaining toasted oats and raisins. Mix on low speed or by hand until completely combined.

Pour the mixture into a greased 9×13 baking pan. Bake at 375 degrees for 25-30 minutes until a toothpick inserted into the center comes out mostly clean. Allow to cool for at least 10-15 minutes, then cut into squares or bars as per your preference. (I usually cut in half on the long axis of the pan, and into eighths on the short axis of the pan, producing 16 bars.)

A note on cooking time: You will want to adjust baking time to your preference. For a gooier, chewier bar, use a shorter baking time. For a drier, flakier bar, use a longer baking time.