1. Preheat waffle iron to medium-high. In a large bowl, combine flour, baking powder, and salt. In a medium bowl, mix eggs, milk, and butter together, then add to flour mixture and stir just until combined (batter will be a little lumpy). Add oats, cinnamon, and sugar and mix just until combined.
2. Using a pastry brush, coat grids of waffle iron with oil. Pour 1 cup batter at a time onto center of grids and close iron (or add batter according to waffle-iron instructions). Bake until golden brown, 4 to 6 minutes. Use a fork to lift waffle off grids and serve immediately.
Note: Nutritional analysis is per waffle.