This is an easy outing, ~5 mile loop, around the lake (not quite, only at the west end you'll see the lake, and the great view of Mt Hood). Sno-park pass required at the road end parking lot. Hike in to the closed road. The summer trail is even shorter.
Winter is a great time for snowshoe and CX ski. Lots of people, but when we arrived around 9am, less than 10 cars. When we left around noon, the big parking lot was almost full.
With the recent rain, lots of new fluffy snow. Lovely.
https://www.outdoorproject.com/adventures/oregon/cross-country-skiing/trillium-lake-loop-trail