A very easy and nice place for wildlife watching in Grand Teton National Park is at the Oxbow Bend Turnout. It's conveniently located along the Snake River, plenty of parking and over the course of a few hours we saw deer, elk, pelicans, even a river otter ... and some light rain.
Since we came with the RV, we had dinner right there on the river to envious looks from other wildlife watchers.
We heard from others that evening that they saw a moose cow with calf at the nearby Willow Flats turnout. There's plenty going on and to see here. It takes a little bit patience, but you won't get bored.
Most of my wildlife photos are a bit blurry due to being taken at dusk. When going on a trip like this, remember to bring your tripod ...