Preheat oven to 350 degrees F and line and baking sheet with parchment paper. Set aside.
In the bowl of a stand mixer, combine butter, oil, and brown sugar and mix on high for about a minute, until the sugar has dissolved. Add eggs, applesauce, and vanilla; mix for an additional minute until the batter is light and fluffy.
To the bowl add the oats, bran flakes, both flours, baking soda, cinnamon, and salt. Mix for 30 seconds until the flour is mixed in. The dough will be moist and sticky.
Fold into the dough the desired add-ins listed above. Scoop 3-4 tablespoons of dough and mound on the prepared baking sheet. Flatten dough slightly with the back of a spoon. Bake 10 to 12 minutes or until lightly golden brown.