McDonald's conversion to fresh beef in its Quarter Pounders is speeding up. The company said the switch is now in effect at 3,500 restaurants in cities including Miami, Orlando, Atlanta, and Nashville, reports Reuters. By May, the change will be in effect in most of its 14,000 US restaurants, per the AP. The chain's "Signature Crafted" burgers also will use fresh beef, though Big Macs and other burgers will continue to use frozen patties. The move is part of McDonald's attempt to shed its junk-food reputation and to counter competitors such as Wendy's, Chick-fil-A, and Shake Shack. (More McDonald's stories.)