In a large bowl, combine the oats, whole wheat flour, all-purpose flour, brown sugar, baking soda, baking powder, and salt. In a separate bowl, whisk together the beer, buttermilk, melted butter, and vanilla. Make a well in the dry ingredients and pour the wet ingredients into the well. With your fingers, stir the batter from the middle of the bowl to the outside, until it's well mixed. It will look more like cake batter than bread dough.