2010-2014 Outback:
--stock: 225-60-17, awful size, only Geolander AT-S available, which runs a bit small
--easy upgrade: 235-60-17 per several members, Cooper Discoverer AT3
--easy upgrade: 225-65-17, which is what I have. Geolander AT-S, Pirelli Scorpion ATR, and Maxxis 771. BFG TA KO2 supposed to be available soon.
Although I have 0.5" spacers, which results in the rear wheels being pushed forward, the tire fits fine.
--tough upgrade: 235-65-17. This is reputed to be the tallest that can fit. I have test-fitted such a tire and it was literally mm from the wheel well, so a no-go with spacers. But should fit a stock car or a car that has the Primitive rear kit.
Think twice about: going beyond 235-60-17 on an H4, unless very steep hills and high elevations are not on the radar.