Yep, for this rcipe, quick rolled oats will work just fine. You are basically using the rolled oats as a textural filling agent that adds bulk to the crisp topping. It becomes crunchy as it interacts with the other topping ingredients, (i.e. fat, flour, sugar) under heat. I ovten omit the recipe and just wing it as you will get to know the feel of the raw crisp topping as you make it a few times. It's really pretty easy, and forgiving. Unlike cake, crisp toppings don't require exact measurements, which is a good thing. It allows you to play with the ingredients and tailor your topping to the filling underneath.
Seeeeeeya; Goodweed of the North