Ok, so I FINALLY decided to stop wasting my money on the Wilton cookie icing and try to make my own. I LOVE it, and it's so much cheaper to make!! My question is, the recipe I used contains milk. It's basically just powdered sugar, milk, and corn syrup. Since it contains milk, do the iced cookies need to be stored in the refrigerator, or does the sugar preserve them enough? If it is ok to store them outside of the refrigerator, how long would you think they remain 'fresh' for?

the sugar and corn syrup (just a different kind of sugar) will preserve it.

no worries -- unless you have counter surfers in the house (husband, children, dog, cat, me)

staleness - depends upon how long out side, humidity, temperature, etc.

got a good cookie jar or cookie container?

(of course -- are they really doing to last "that" long? see surfer comment)

American buttercreams don't require refrigeration because the large amount of sugar (which is hygroscopic) in the recipe controls the "water activity" in the small amount of milk used.

Whether your recipe is shelf stable depends on the amount of liquid to the amount of sugar/s, not just the ingredients used in the recipe.

So mostly sugar/s and a bit of milk should be fine.

HTH

I have used milk in my buttercream for years...grandmother and aunt used it even longer than me, and we have never had any issues with spoils, melting, etc..... Has always held up for me.

Thank you so much for all your help. It only has 2 tsp of milk per 1 cup and 2 tsp of powdered sugar/corn syrup. And like you said...they taste so good I am sure they won't be lying around for long!