These nostalgic gluten-free oatmeal cookies are so soft and chewy, with great flavor from molasses and warm spices. Delicious as-is or topped with icing! I give two recipe variations so you can make these nut-free if you'd like.
Preheat oven to 350°F and line a large baking sheet with parchment paper.
If making the iced oatmeal cookies, pulse the rolled oats in the food processor 10-15 times until some of the oats are finely ground and some are just coarsely chopped. This will give the cookie a fluffier texture that is only moderately textured on top, making it ideal for dipping in the icing. If you're not going to ice the cookies, skip this step. Set the oats aside.
In a medium mixing bowl, sift together the almond flour, tapioca flour, sweet rice flour, baking soda, baking powder, cinnamon, nutmeg, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment or a large mixing bowl with a hand mixer, cream the butter and sugars together starting on low speed and increasing to medium-high speed, until light and fluffy, 3-5 minutes. Scrape down the sides and add the egg, molasses, and vanilla extract and beat until just combined, scraping down the sides as needed.
With the mixer on low speed, slowly add the sifted flours until just combined. Add the rolled oats and beat for a few seconds until evenly distributed.
Scoop the dough into 1½ tablespoon-sized balls onto a baking sheet (I use the OXO medium cookie scoop and it makes exactly 18-21 cookies, depending on oat v almond variations).
Bake immediately or for thicker cookies, chill the cookie dough in the fridge for 1 hour or in the freezer for 15 minutes, until firm. Working in batches, place the chilled cookie dough balls 2 inches apart on the parchment-lined baking sheet. Skip chilling and space cookie dough directly on the parchment-lined baking sheet for thinner cookies.
Bake chilled cookies for 13 minutes or room temperature cookies for 10-12 minutes, until the edges are set, but the center still looks slightly underbaked. If you did not pulse the oats in step 1, add 1 minute to the baking time. Let cool for 5 minutes on the baking sheet before transferring to a cooling rack with a thin spatula to cool completely before icing.
When the cookies are completely cooled, prepare the icing.
In a small bowl, mix together the powdered sugar, vanilla, salt, and ½ tablespoon of milk. Add more milk, 1 teaspoon at a time, just until the icing is smooth but very thick. When drizzled back onto itself, the icing should hold its shape for a few seconds before settling back into the bowl. Take a cooled cookie and very lightly dip the top of it in the bowl of icing a few times until it has the desired amount of icing. Imagine gently tapping the cookie on the icing letting any excess drip off before turning it over. This will produce the crackly top. Serve immediately or return to the wire rack to let the icing set for an hour before stacking cookies.
Notes
Nut-Free Version: For a nut-free version, follow the same recipe instructions, replacing the almond flour, sweet rice flour, and tapioca flour ratios listed in the recipe with this blend and continue as instructed:
81 g (¾ cup) Bob's Red Mill gluten-free oat flour
30 g (3 tablespoons) Bob's Red Mill sweet rice flour
28 g (¼ cup) Bob's Red Mill tapioca flour
Dairy-Free Option: replace the unsalted butter with dairy-free plant butter and the milk with dairy-free milk, such as oat milk.Baking time: When ready to come out of the oven, the edges of the cookies should be set to the touch, while the centers appear moist and underbaked. Take care not to overbake the cookies, as they'll continue cooking on the baking sheet and the oats will soak up more moisture as they cool. Overbaked cookies will be cakier and less chewy, but icing adds moisture and can easily save an overbaked cookie. On the other hand, if you underbake the cookies, they'll be too soft to dip in the firm icing without breaking against the tension. If you find this happens, you can drizzle the icing over the cookies for the same flavor.Freezing the Dough: Use a cookie scoop to roll the cookie dough into even balls and chill on a baking sheet in the fridge for an hour or freezer for 15 minutes. Once firm, transfer the cookie dough balls to a gallon freezer bag and store in the fridge for up to 5 days or in the freezer for up to 6 months. If you've stored the cookie dough in the freezer for longer than 30 minutes, you'll also need 1-2 additional minutes of the baking time. When baking the cookies directly from long freezer storage, they will bake up thicker than pictured here. Alternatively, let the dough sit at room temperature for 30 minutes before baking if you don't want your cookies to bake up thicker.