Preheat your oven to 350 degrees F. Line baking sheets with parchment paper.
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
In a separate medium bowl, whisk together the gluten-free flour blend, baking soda, salt, and cinnamon.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix.
Stir in the gluten-free rolled oats and raisins by hand until evenly distributed throughout the dough.
Drop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart. For thicker cookies, press the dough balls down slightly.
Bake for 10 to 12 minutes, or until the edges are lightly golden brown and the centers look set but still soft.
Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.
Notes
Use certified gluten-free rolled oats to prevent cross-contamination.
If your gluten-free flour blend does not contain xanthan gum, add 1/2 teaspoon to the dry ingredients for better binding.
For dairy-free cookies, substitute the butter with an equal amount of firm, dairy-free butter sticks.
Chill the dough for 30 minutes before scooping if you prefer thicker cookies that spread less.