The test is limited to just 14 restaurants, but it represents the biggest potential change to McDonald's menu in decades.
McDonald's has long relied on an extensive network of suppliers who make, freeze, and ship beef patties to its more than 14,000 restaurants in the US.
Expanding the test would require a massive shake-up to its supply chain.
The test, first reported by Jonathan Maze at Nation's Restaurant News, is limited to Quarter Pounder patties used in the Quarter Pounder with Cheese, Double Quarter Pounder with Cheese, Bacon Clubhouse and the Homestyle Burger, which is a regional burger in the Dallas-Fort Worth area.
McDonald's spokeswoman Lisa McComb said it's too early to tell whether the test will be expanded.
"Like all of our tests, this one too is designed to see what works and what doesn't within our restaurants by considering the operational experience, consumer response, price points and other important information which may inform future decisions," she told Business Insider. "It's very premature to draw any conclusions from this test."