In a medium mixing bowl, whisk together the flour, oats, cinnamon, baking soda and salt. Set aside.
In another large mixing bowl, cream the butter with an electric hand mixer on medium speed until smooth. Once smooth, add the brown sugar and white sugar and beat until creamed. Once the sugar and butter mixture is creamed, add in the eggs, molasses, and vanilla and beat until thoroughly combined.
Combine the dry ingredients with the wet ingredients and use the hand mixer on low to combine. At this point you can split the dough into batches and keep one batch plain and add raisins to the other. Cover the cookie dough and allow to refrigerate for at least 50 minutes.
Meanwhile, preheat the oven to 350F degrees and prepare baking sheets.
Once the dough has finished chilling, scoop about 2 ½ to 3 ½ tablespoons of dough on the sheets, depending on how large a cookie you prefer. Bake the cookies between 10-15 minutes until they are only slightly browned on the sides. Once baked, remove from the oven and allow to cool. Serve slightly warmed or at room temperature.