Preheat your oven to 350°F (175°C).

In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.

Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.

In another bowl, combine the flour, baking soda, salt, and cinnamon. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Stir in the rolled oats.

Drop rounded tablespoons of dough onto ungreased baking sheets, spacing them about two inches apart.

Bake for 10-12 minutes or until the edges are golden brown. Let cool on the pan for a few minutes before transferring to a wire rack to cool completely.

Once cooled, spread a generous layer of marshmallow creme on the flat side of one cookie and sandwich with another cookie.