The biggest burger maker in the free world wants to find out if it can cut the mustard in Moscow, but only after it goes Hungary.

McDonald's announced Friday it will open the first of a string of eateries in downtown Moscow next year.It may not mean golden arches in Red Square, but it will mean Muscovites can munch fries, slurp shakes and gobble "Big Maks" just like their Western counterparts, courtesy of McGlasnost.

"I think the McDonald's in Moscow will be the highest volume McDonald's in the world," predicted George A. Cohon, president of McDonald's Restaurants of Canada Ltd., after signing a joint pact with the Moscow city government.

Meanwhile, the first McDonald's in a Soviet bloc country opens its doors Saturday in Hungary. The Budapest burger emporium was dedicated on Friday.

Last month, McDonald's opened a restaurant in Belgrade, Yugoslavia, its first in a communist nation. Impatient customers waiting in line on opening day became so unruly that police were called.

Although five more restaurants are planned for Belgrade, Moscow could be the big enchilada for McDonald's, which had worldwide sales of $14.3 billion last year.

Cohon and Vladimir I. Malishkov, chief of food services for the Soviet capital, signed an agreement for the creation of up to 20 fast-food eateries in Moscow and the building of a commissary to process beef, potatoes and other foods McDonald's uses.

"A Big Mac, our world-famous sandwich, will taste the same in Moscow as it does in Toronto, or Tokyo, or Rio, or New York," Cohon vowed at a news conference in Moscow's city hall.

The agreement, which gives McDonald's of Canada a 49 percent share in the Soviet-controlled joint firm, is the latest business venture concluded by the Soviets with a foreign company, and th first with a Canadian firm.

Last year, the Kremlin enacted a new law on joint ventures in a bid to woo capital, technology and expertise from abroad. The reform is part of changes enacted under Soviet leader Mikhail S. Gorbachev designed to improve the quality and quantity of consumer goods.

Pepsico Inc. last September signed a contract to open two Pizza Hut restaurants in Moscow in a joint venture. A New Jersey company called AstroPizza brought a van into the capital this month to serve pizza to Soviets and foreigners, and plans to open a joint venture restaurant in Moscow later this year.