Originally Posted by Alwaysbehind
Close the garage door.
Always, although I find your answer to be funny as heck, I have to say that cats have a way of finding their way into places like garages even when the doors are closed.
Rosebud, no advice, sorry. Cats are like mice; they can squeeze through places you wouldn't think they'd be able to fit.
If their previous home was a garage, they're just doing what's familiar.
Just make sure to keep their food, water, and any bedding in the barn, and eventually they'll most likely decide to move on their own.