I am often mistaken for a vegetarian, because I don't eat much meat and will pick a veggie entree at most restaurants, even when meat is offered. Really I'm just a squeamish omnivore - learning about factory farming (from Michael Pollan's Omnivore's Dilemma and others)ruined my appetite for most chicken, beef, and pork.
Which is why I was so pleased to find bison for sale at my local cheap grocery. Burgers and fries are a weakness for me; but with wheat off the table (a story for a different day) I'm getting by just fine with the occasional plate of bison burger on a gluten-free roll, with a side of sweet potato oven fries.
Although I did find a package of "grain-fed bison" once (why? why?!), most bison are range-raised, naturally hormone and antibiotic free. Some ranchers do finish them briefly on corn in a feed lot; but mainly they spend their lives outdoors much as they did hundreds of years ago, before being driven nearly to extinction. Back up to about a quarter of a million across north America, they roam under supervision, helping restore ecosystems while grazing.
In addition to being more sustainably raised, bison are leaner than beef and have less cholesterol as well. And as long as you don't overcook the meat, it serves up juicy and full of flavor.