If you've got a full garage and not enough work place, and you should reclaim that workplace by moving circumstances to the garage, think about these options. First, organize what's in the garage:
If you've got too many home office supplies to hold or not enough space in a garage or attic, consider an outbuilding, there are various options, including some buildings that snap together requiring no building knowledge at all. Others can be acquired on the cheap if you can put it together yourself, including an 8 X 10 foot metal building for under $200 I saw recently inside my local store. You may be able to find a second hand one too, by looking within the classified ads of your respective local paper. If you might have the money, and that you do not have enough room on your lawn equipment, this might be the right solution.
Tip: Outbuildings which can be tall enough to wear over your backyard fence may necessitate a building permit. Check with the local authorities before you build anything that is permanent.
Now you've gained a little room within the garage for the "stuff", you can begin moving it there. Before you do though, you should think about getting rid of old printers you do not use, scanners you don't need, and even old computer towers which are not quite dead, but will be soon. There's no reason to store items you won't need later.
With that done, consider what has to be moved out of the office. Box items together in see-through plastic bins if you can afford them, and write externally what's included. You can have one large bin for old tax papers, one for old contracts and reciepts, then one for cables you only need to access rarely (Ethernet, Coax, USB). These bins, once filled, can easily be moved and stacked, so they use up very little room in the garage.
Now you could start moving the larger items. If possible, purchase shelving (or free a preexisting shelving unit) to keep only office-related items. You can put extra paper here, old computer towers, photo printers you rarely use, and similar items. While you're inside the zone, check out what's inside your office that is not office-related and move it too. Just because that's where you've always stored the kitten food, the additional linens, winter coats, and the like doesn't mean that is where it has to stay!
So spend per day getting organized; trust me, you'll are more effective, be a little more relaxed, and convey better work! There's nothing like a clean office to inspire!