I was just planning to submit a trip report of our day trip from GNP to the National Bison Range, so I hope it answers your question:
"We scheduled in a non-hiking day so we could drive down to the National Bison Range near Moiese. The drive along Flathead Lake was gorgeous and it took us about 2 hours to get there from West Glacier. The cost is $5 per car, but is no additional cost if you have a NPS annual pass. The Visitor’s Center contained some excellent exhibits. Don’t miss the wall of “dots” depicting the number of buffalo in 1850 as opposed to today and the “stack of racks” outside. There is also a relief map showing where the bison herds are on that particular day so you know where to look for them on the loop road. (There are supposed to be about 400 head of bison on this reserve, but we only saw about 40-50 head.) It took us about 2 hours to drive the loop and, in addition to having a bison herd walk around our car, we spotted deer, antelope and elk. There are a couple places where you can get out of the car for short hikes and we did the one to the highest point in the park—good hike, great views! There is a large, well-maintained picnic area in the park where we enjoyed our picnic lunch. If you can devote a day from your GNP trip, I highly recommend the National Bison Range."