Mix all dry ingredients together in a large mixing bowl.
In a separate bowl combine milk, eggs, and vanilla.
Add the wet ingredients to the dry and mix just until blended. Stir in the oil; if too runny, add 1/4-1/2 cup more flour.
Slice strawberries. Preheat waffle iron.
Add half cup blueberries and half cup strawberries to the batter; stir gently until just combined.
Pour 1/2 cup of the waffle mixture onto a hot waffle iron and cook until done. Repeat until all batter has been used.
Serve waffles topped with yogurt and remaining berries.