From bean + -burger.
beanburger (plural beanburgers)
- A vegetarian burger made from beans.
1989 November, Drew DeSilver, Jan Gahala, “What is that stuff?”, in Vegetarian Times, →ISSN, page 44:Okara adds texture to soups, stews, casseroles, savory pancakes and baked goods, or it can be made into beanburgers.