J. Robert Schultz, formerly senior vice president of Marriott Corp., has taken the reins at Micros Systems Inc., a Beltsville-based producer of electronic point-of-sale systems and computerized cash registers.

As the company's new president and chief executive officer, Schultz, 50, replaces Jeffrey C. Rice, who had held Micros Systems' top management position since the company's founding in 1977. Rice was scheduled to leave the company after its annual meeting last weekend.

Schultz, credited with righting Marriott's beleagured theme-park division, and formerly the executive vice president in charge of Marriott's $800-million-a-year contract food services operations, said he will supervise a major expansion planned by Micros Systems in the United States and Europe.

Micros Systems produces electronic equipment including systems that link sophisticated cash registers to other data management systems such as inventory control and accounting. The systems are used in the hotel, retail, service station and food-service industries.

Schultz said in an interview that while he has little experience in high-technology industries, his familiarity with the hospitality industry and his skills in finance and marketing are "the kind of basic business skills needed to turn Micros Systems into a much larger company."

Edward T. Wilson, the company's chairman, agreed and noted that Schultz's appointment has been received enthusiastically by the company's management staff.

"The businesses I've run have been very profitable," said Schultz, who helped fix cash-flow problems of the Stamford, Conn., General Housewares Inc. in the early 1970s, and who turned around a substantial loss at Barwick Industries Inc., a textile manufacturer in Atlanta, between 1975 and 1979.

Micros Systems saw a 56 percent increase in profitability in 1984 over 1983. The Beltsville firm had revenue of $22 million and $732,000 in profits in the fiscal year ended June 31, 1984.

"I am not there because there's a problem," Schultz said. "I'm there for expansion.