Preheat a waffle iron to medium-high. Preheat the oven to 200 degrees F (to keep cooked waffles warm). Whisk together the flour, cornmeal, oats, wheat germ, if using, baking powder, salt and baking soda in a large bowl. Whisk together the buttermilk, oil, sugar and eggs in another bowl. Pour the buttermilk mixture into the flour mixture and gently stir until just incorporated (it's okay if there are some lumps).
Lightly brush the top and bottom of the waffle iron with oil. Fill the waffle iron about three-quarters of the way full (some waffle iron should still be showing). Close the lid gently and cook until the waffles are golden brown and crisp, 6 to 7 minutes. Keep the cooked waffles warm in the oven or covered with foil on a plate while you make the remaining waffles.
Top each waffle with yogurt and fruit preserves.