Reagan administration officials say they will support continuing the government's flexible work hours program if Congress outlaws the awarding of holiday "bonuses" worth two hours' pay to feds working four-day, 10-hour weeks.

For the past six years Uncle Sam has been experimenting with alternative work schedules that permit agencies to put workers on flexible, or compressed, schedules. The schedules are set up to provide increased service to the public.

The flexitime experiment expires in July unless Congress and the White House extend the legislation. About 300,000 federal workers, many of them here, are on schedules that permit them to come to work as early as 6 a.m. or as late as noon. Some have chosen to work four 10-hour days a week.

Officials of the Office of Personnel Management told the Human Resources subcommittee of the House Post Office-Civil Service Committee yesterday that they generally favor flexitime.

But OPM administrator Donald Devine says the administration is troubled by the fact that employes who work 10-hour days get an extra two hours of pay when a holiday falls on one of their regular workdays.

Other federal workers are paid for only eight hours on holidays, Devine said. Government workers now get nine paid holidays a year. A 10th, a day in memory of the Rev. Martin Luther King Jr., will be added next January.

Devine suggested that employes on the four-day schedule be paid for only eight hours of leave when they are off for a holiday, or that they make up the two hours by working some other time.

Subcommittee members said OPM was nit-picking, to put it kindly.

Rep. Frank Wolf (R-Va.), who is sponsoring a bill to extend the flexitime experiment, said studies have shown that flexible work hours improve employe morale, productivity and service to the public. The General Accounting Office said its recent investigations have confirmed that the benefits of flexitime outweigh any drawbacks to the program.