After more than 60 years of dishing out beef burgers, a Canadian fast-food chain has found new success in an unexpected product: a patty made from peas, mung beans and beets.

A&W Food Services of Canada Inc. (AW_u.TO), the country’s second-largest hamburger chain, is tapping into growing demand for plant-based protein by becoming the first national burger chain to offer California-based Beyond Meat’s burger on its menu in July.

The Beyond Meat burgers sold out nationwide in a matter of weeks, said Chief Executive Officer Susan Senecal. The veggie burgers will be back in stock across Canada Oct. 1.

“It became even more popular than we had expected,” Senecal said in a telephone interview from Vancouver. “Plant-based protein has gained in popularity and it really is something people are very interested in.”

A&W is the latest meat-focused company that sees growing opportunities in plants as some consumers turn away from traditional protein amid concerns about environmental impact, animal welfare and maintaining a healthy diet. Tyson Foods Inc., the largest U.S. meat producer, in 2016 acquired 5 per cent of Beyond Meat, which has also gotten the backing of billionaire investor Bill Gates. Maple Leaf Foods Inc., Canada’s largest packaged meat company, is now stocking shelves with plant-based imitators after acquiring vegetarian producer Lightlife Foods.

A&W’s Beyond Meat burger builds on the company’s strategy to focus on better ingredients, Laurentian Bank Securities analyst Elizabeth Johnston said in an email. While these new products have generally been positive for organic growth, it’s too early to quantify the potential impact of the burger, she said. The A&W Revenue Royalties Income Fund, which invests the securities of A&W Food Services, is up 7.3 per cent this year and hit a 15-month high in August.

Five years ago, A&W started to home in on growing consumer demand for more information and transparency about their food, said Senecal, noting the chain now offers beef raised without any added hormones or steroids and chicken raised without antibiotics. The plant-based burger builds on consumer desire for more natural foods and the company is constantly monitoring how the trend develops, she said.