A crowd of 20,000 gathered near the 1.5-km barbecue in the city's park, paying a mere $3 to sample the meat cooked on six tons of charcoal.
"It's all so beautiful. It's a record" the agency quoted the U.S. adjudicator from the Guinness World Records, Danny Girton, as saying.
The event organizers called firefighters to light the barbecue and to ensure safety.
The feast was organized by Uruguay's National Meats Institute (INAC) to promote the country's image as a major beef producer.
"Uruguay is very small, it's not known for many other events, possibly football, so we have to use these kinds of gimmicks so people find out where Uruguay is and what it has to offer," INAC's vice president, Fernando Perez Abella, told the Mercopress agency.
The previous record was set in Mexico in 2006, when 8,000 tons of meat was cooked.
