McDonald’s, the second-largest fast food chain in the U.S., on Tuesday announced that thousands of its domestic restaurants would offer fresh beef burgers by the middle of the year. 

The fast-food giant said it switched out frozen patties in exchange for fresh beef in its Quarter Pounder burgers at about 3,500 of its locations including cities like New York and Los Angeles. 

The company looked to cover 14,000 locations across the U.S. by the beginning of May. Cites in Hawaii and Alaska would not be a part of the changes, according to CNBC.

"The switch to fresh beef quarter-pound burgers is the most significant change to our system and restaurant operations since All Day Breakfast [in 2015]," McDonald's USA President Chris Kempczinski said in a news release. "McDonald's is a burger company and there is no better place to start than with our burgers."

"Over the past two years, we have been listening to our customers and evolving our business to build a better McDonald's. We are proud to bring our customers a hotter and juicier quarter-pound burger at the speed and convenience they expect from us," he added. 

Joe Jasper, a 40-year partner who owns 20 franchises in Forth Worth, Texas, has been instrumental in McDonald’s new beef initiative, a four-year-long project. Jasper’s restaurant was one of the first to test out the patties.

McDonald's has been selling fresh beef alongside frozen patties at many of its locations for about a year. The shift comes as part of the company’s effort to remain competitive amid a fast-food market threatened by gourmet-style burger joints like Shake Shack, which often offer healthier, high-end options.

Speed has also been part of the brand’s focus as it has optimized the way customers receive their food while on the go.

"If it slows down the drive-through, that's the critical part of our business," said Kempczinski. "And so we just had to spend a lot of time really making sure that as we were cooking only when someone ordered, we'd figured out a way to do it that wasn't going to slow down service time."

The company said it expects the changes fully completed by June.