While Subaru’s all wheel drive seems pretty capable of making it through almost any snow I’ve been through in the Northwest, if the police want to require chains or snow tires, they can. But if you need chains, the Subaru manual recommends against tire chains (not very helpful). The dealers don’t seem to know much either. To make things worse, the higher end Outback’s with larger tires (P225 55R17) have so little clearance that you can’t use higher end chains which are easier to put on. There’s not a lot of information on the Web either.
Cheap cable chains seem to be the best solution. I spent $32, got the thinnest cable chains I could for that tire size with the rubber attachments for tightening them down to prevent damage inside the wheel hub. A flashlight isn’t a bad idea if you have to put them on at night. Then throw them in the back of the car when you go over the passes and use the Subaru’s sport drive. I’ve yet to need them.