In a bowl, stir together oat bran, flour, baking powder, and soda.
In another bowl, beat egg and oil to blend with buttermilk and milk; add liquids to dry ingredients and stir until evenly moistened.
In an oiled waffle iron heated to medium-high, add enough batter to fill about half full.
Cover and bake until waffle no longer steams and is crisp and golden, 4 to 5 minutes.
Lift out waffle and season to taste with butter and syrup.
Repeat to bake remaining waffles.