The problem, of course, is that you’re working hard during cross-country skiing, particularly so when going uphill. At that stage, you’re not generating enough airflow to clear the warm, moist air getting trapped behind your goggles. I sometimes have the same problem when bicycling up a long, slow hill. I get to the top and am half blind.
Most downhill ski goggles would be particularly prone to this, so I’m not surprised you’re having problems, even though the wind you mention should help ventilate them. You might apply one of several anti-fog coatings to the goggles. Additionally, Scott makes a goggle called the Split Six that is expressly designed to reduce fogging. It uses a non-fog coating and extra vents to help ensure your view of the world is clear. They’re $50.
Glacier glasses might help. But I should think most of them would be too dark for winter use, even on snow. Moreover, the side flaps might cause the same problem you’re having now.
I’d try some sport shieldssemi-wrap-around sunglasses. These would protect your eyes from blowing snow yet have enough ventilation to stay clear under all but the most extreme fog-inducing conditions. Plus, lots of these sport-style glasses have interchangeable lenses, so you can use the lens most suited for that day’s light conditions. Some examples: the Dragon Rake ($99), Smith Voodoo ($99), and Rudy Project Kerosene ($125). All are good-fitting, well-made glasses with excellent lenses.
Check out the Gear Guy’s sports-shield picks: , , and .