Whisk the eggs in a large bowl. Add the milk, oil, and vanilla and whisk well to combine.
Combine 3 cups flour, baking powder, and salt in a medium bowl. Slowly add to the egg mixture. If your batter is too runny, add more flour as needed.
Carefully spoon batter into the preheated waffle maker. Shut the lid and cook for 3-5 minutes, depending on desired finished consistency (soft or crunchy - I like to cook mine for 3 minutes so they are a little soft and pale. That way, I can toast them up later and they won't be too dry.).
Lay the cooked waffles in a single layer on a baking rack. Allow them to cool completely. Once cool, carefully lay them in a bread bag to freeze if you wish to store them for later.