In a medium bowl, mix milk, oil, eggs, brown sugar and vanilla, whisking to combine. Stir in the wheat bran and oats. Allow this to sit for 5 minutes.
Preheat the oven to 400°F.
Stir in the flour, cinnamon, salt, and baking powder. Fold in the orange peel.
Line a 12 cup muffin tin. Distribute the batter between the 12 cups. Bake for about 15 minutes, test them for doneness with a toothpick. Leave the muffins in the pan for 5 minutes. Remove them and cool completely on a wire rack.