Preheat oven to 350°F and line baking sheets with parchment paper.
In a large bowl, cream together softened butter, brown sugar, and granulated sugar until light and fluffy, about 3 minutes. Beat in eggs and vanilla extract.
In a separate bowl, whisk together gluten-free flour, baking soda, cinnamon, and salt. Gradually add to butter mixture and mix until combined.
Stir in oats and raisins or chocolate chips until evenly distributed. Let dough rest for 10 minutes.
Drop rounded tablespoons of dough onto prepared baking sheets, spacing them 2 inches apart. Flatten slightly with the back of a spoon.
Bake for 10-12 minutes until edges are golden but centers still look slightly soft. Cool on baking sheet for 5 minutes, then transfer to a wire rack to cool completely.