The National Bison Range is about 40 minutes away from Big Arm State Park. We went there a couple of times during our camp hosting gig and saw bison (of course!), bears, elk, and deer.
The range has two loop drives: one that takes about 45 mins to an hour, and the other that is twice that long. It's worth it to go on the longer drive because it takes you to more of the areas that you are apt to see wildlife.
Stop in the information area and ask the ranger where people are seeing the critters. Then keep your eyes out! There's lots to see. Plus the hill and valley views are breathtaking as well!