Cream butter and both sugars until light and fluffy. Beat in eggs one at a time and then stir in vanilla. Add flour, baking soda, salt, and cinnamon and mix until fully incorporated. Stir in oats and additions of choice.
We've used this basic recipe with a ton of different add-in options:
1 cup dried cranberries, 1 cup chopped pecans, and 1 cup white chocolate chips; OR 1 cup raisins and 1 cup chopped walnuts; OR 1 cup semisweet chocolate chips and 1 cup chopped pecans; OR 1 bag butterscotch chips; OR 1 bag Heath toffee bits