Mix buttermilk and oats in a medium bowl; let stand for 15 minutes.
Whisk whole-wheat flour, all-purpose flour, wheat germ (or cornmeal), baking powder, baking soda, salt and cinnamon in a large bowl.
Stir eggs, sugar, oil and vanilla into the oat mixture. Add the wet ingredients to the dry ingredients; mix with a rubber spatula just until moistened.
Coat a waffle iron with cooking spray and preheat. Spoon in enough batter to cover three-fourths of the surface (about 2/3 cup for an 8-by-8-inch waffle iron). Cook until waffles are crisp and golden brown, 4 to 5 minutes. Repeat with remaining batter.