McDonald's flips to fresh beef in 3,500 U.S. restaurants

McDonald's Corp said on Tuesday that it had begun serving fresh beef Quarter Pounders and other premium burgers at about 3,500 restaurants in the United States, and most of its other U.S. locations will follow suit by May.The fresh beef expansion comes as McDonald's is improving food quality and increasing menu variety to counter competition from older rivals such as Wendy's Co as well as more premium chains like Chick-fil-A, In-N-Out and Shake Shack Inc.One year ago, McDonald's announced plans