In the winter, Going-to-the-Sun Road [1] is plowed to the head of Lake McDonald [2]. From the parking area there, it’s possible to ski as far up the road as stamina permits. The skiing is technically easy, and there’s usually some wildlife around.
Pull off the main drag and follow the Sacred Dancing Cascade hiking trail or ski up to the Trail of the Cedars.
For a longer trip (about 12 miles), ski up Camas Creek Road, take a right at McGee Meadow, and return on the Inside North Fork Road. A final detour through the Fish Creek Campground to Rocky Point adds a couple of miles and a good view of Lake McDonald.
Links:
[1] http://www.moon.com/destinations/montana/glacier-national-park/lake-mcdonald-valley/sights/going-the-sun-road
[2] http://www.moon.com/destinations/montana/glacier-national-park/lake-mcdonald-valley/sights/lake-mcdonald