Preheat your oven to 325 degrees F.
In a medium sized mixing bowl, whisk together the flour, finely ground oats, cinnamon, baking powder and salt. Set aside.
In the bowl of an electric mixer, fitted with the paddle attachment, cream the butter and the sugar for two minutes on medium-high speed.
Scrape down the sides of the bowl and begin to add the eggs on medium speed, scraping down the sides and bottom of the bowl between addition. Stir in the vanilla.
With the mixer on low speed, add 1/3 of the flour mixture, followed by 1/2 of the milk. Repeat the additions, 1/3 cup flour mixture, 1/2 milk and the final 1/3 cup flour mixture. Only mix until the flour mixture is incorporated, about 30 seconds. Scrape down the sides and bottom of the bowl and mix again for another 20 to 30 seconds on low.
Toss the chocolate chips in one tablespoon flour and then fold the chocolate chips into the cake.
Evenly divide the cake batter between the three 8-inch pans or the four 6-inch pans (20 oz. in each 8" pans and 15 oz. in each 6" pan). Bake the cake layers (either size) at 325 for 28 minutes or until a toothpick inserted in the center of the cake comes out with a few moist crumbs on it.
Let cool for about 15 minutes in the pans before inverting onto a wire rack to cool completely.
Once cooled completely, each layer can be wrapped in plastic wrap and stored in the freezer for up to a week. For longer storing, also wrap in foil.