Preheat your oven to 350°F (175°C). Line your baking sheet with parchment paper for easy cleanup.
In a large mixing bowl, beat together the shortening, brown sugar, and granulated sugar until the mixture is light and fluffy.
Add the egg, water, and vanilla extract to the creamed mixture. Beat until well combined.
In a separate bowl, whisk together the all-purpose flour, salt, and baking soda. Gradually add this mixture to the wet ingredients, stirring until just combined.
Gently fold in the quick-cook oats and Butterfinger baking bits until evenly distributed throughout the dough.
Using a cookie scoop or spoon, drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden. The centers may look slightly underbaked, but they will continue to set as they cool.
Remove the cookies from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. Enjoy your freshly baked Butterfinger Oatmeal Cookies with a glass of milk or your favorite beverage!