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In a startling turn of events this morning, fast food giant McDonald’s announces that the chain is starting to introduce fresh beef into its restaurants, gradually switching over from its frozen stock. CNBC reports that “The burger giant… has already brought fresh beef Quarter Pounder patties to about 3,500 domestic restaurants so far and it plans to reach some 14,000 U.S. locations by early May.”

The switch to fresh beef has been in the works for about four years, as fast food outlets like McDonald’s try to find ways to present healthier and less processed options in an increasingly competitive market. McDonald’s has already tried to slim down its Happy Meals and avoid antibiotics in its chicken nuggets. Last month, Wendy’s called out McDonald’s “flash frozen patties” versus Wendy’s fresh ones specifically in a shade-drenched Super Bowl ad, referring to the veteran chain as the “Frozen Arches.”

While the fresh patties will cook faster than frozen ones, the transition will be a costly one for McDonald’s, requiring changes in storage and shipping. CNBC says “McDonald’s suppliers spent upwards of $60 million updating their supply chain to transition from frozen Quarter Pounder patties to fresh ones”—clearly, a gamble that McDonald’s thinks will pay off. But tinkering with such a tried-and-true, decades-long classic like the Quarter Pounder certainly will not be without its risks—not unlike messing with the beloved Coke formula, and look how that turned out.

Still, CNBC notes that “After the test of fresh beef in more than 400 restaurants in Texas and Oklahoma, the company said it received a 90 percent satisfaction rating from customers as well as a 90 percent intent to repurchase rate.” No word yet on the transitional fresh/frozen status of McDonald’s non-quarter-pound patties—for Big Macs and traditional cheeseburgers.