Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets.
In a large bowl, cream together the shortening and sugar until light and fluffy. Add the eggs one at a time, beating well with each addition, then stir in the vanilla and sour milk. Combine the flour, baking powder, baking soda, salt and cinnamon, gradually stir into the creamed mixture. Finally, stir in the rolled oats, and your choice of additions. Drop by rounded spoonfuls onto the prepared cookie sheets.
Bake for 12 to 15 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.