Is a box of gluten-free instant oatmeal the same thing as quick-cooking oats?
No. Don't use that recipe.
If the package says they are gluten free then they are gluten free. Oats are gluten free but some are processed on or with equipment or in a plant that processes other grains To determine if they are quick cooking look at the directions if they take less than 5 minutes to cook they are quick cooking. If they just use boiling water they are instant if they take more than 20 minutes they are rolled or "old fashioned" oats.
As long as they are not flavored , all should be well .
Yes, the gluten-free instant oatmeal is the same is the ordinary instant oats.