Onions and oil are mentioned in the instructions but not in the ingredient list - hints about quantity?
I'd say 1 small to medium sized onion and 1/4 cup of olive oil. And though these quantities won't make for a good or bad recipe, I might look for another. Once a recipe is not written clearly, I tend not to trust it. Still, I think these quantities will be just fine. It's not baking after all.