Peter Regner is 37, earns $46,000 a year and is facing unemployment. He expects to be out of work by July, a casualty of Reagan administration budget cuts. After 15 years of relative job security in several government agencies, including the Department of Justice, the CIA and the Federal Mediation and Conciliation Service where he now holds an executive-level post, Regner, who lives in Silver Spring, is understandably anxious about his future.

He devours the classified section of Sunday's newspaper: "I start under the letter A for administrator, continue to E for executive director, then to M for manager. Then I hit every letter in between."

Employment prospects in Montgomery County actually are bright, with the number of jobs in the county expected to increase 12.5 percent by 1982 and many new jobs for white-collar professionals foreseen. Montgomery's 3.2 percent unemployment rate is one of the lowest in the Washington area.

But this is cold comfort at the moment to scores of federal workers who live in the county and are facing loss of their jobs within the next few months. About 2,500 job-seekers turned out for a recent career fair sponsored by the Rockville Chamber of Commerce. Some sought better-paying jobs to help them keep up with the cost of living in expensive Montgomery County; others were federal workers facing layoffs. Surveying the large, well-dressed crowd, chamber president Jim Bowman remarked, "What a sure sign of the times."

In that crowd was Peter Regner, who didn't have much success.

Bill Glaser, a senior technical recruiter for Tracor Inc., a diversified manufacturing company with an office in Rockville, said he was impressed with Regner's credentials but was unable to fit them into a Tracor position.

Regner said he is finding "it's difficult to convince employers that the skills used in the federal government are applicable to the private sector. They tell me my skills are not exactly what they're looking for but I try to convince them I can do the job."

Since February, when rumors first surfaced of a reduction in the program in which he worked, Regner has been scouting the job market.

He "wouldn't mind leaving the D.C. area," but said his wife doesn't want to move: "She enjoys the museums and all that D.C. offers."

For the moment Regner, like many federal workers facing unemployment, is trying to maintain a positive attitude.

"It grows more difficult when you hear you're overqualified for a job because you've managed a $30 million program budget. I want to be able to pay my mortgage," he said.

A senior county planner believes there is considerable room for optimism in Montgomery, where March unemployment statistics, the most recent available, show 10,529 of the 327,495-person work force unemployed. That translates into an unemployment rate of 3.2 percent, far below the national average of 7.6 percent, according to the planner, Lynda Given. The unemployment rate in Prince George's County was 4.4 percent in March; in Northern Virginia it was 3 percent.

Given said a survey recently completed by the Montgomery County Private Industry Council projected an additional 22,110 fulltime jobs in private business and industry between 1980 and 1982, an increase of 12.5 percent. The council is staffed by county employes and directed by a group of private business leaders.

County leaders hope private-sector growth ". . . will offset the shrinking federal job market," Given said.

She believes the figures, gleaned from a survey of private businesses in the county, are "on the conservative side" in light of the new businesses being established along the I-270 corridor in Rockville and Gaithersburg and along Rte. 29 in Silver Spring.

According to the survey report, jobs for professionals such as scientists and engineers and for machine operators, inspectors and precision workers in various industries, including printing and electrical manufacturing, will be most plentiful.

Overall, the survey found, private-sector employment in the county, with an annual increase of 6.2 percent from 1980 until 1982, is more plentiful than what is projected for the state, the Washington region and the nation.

Some of those jobs probably will be available to federal workers who soon will be out of work.

At the National Bureau of Standards in Gaithersburg, 167 employes will be laid off by late summer. By Oct. 1, the Public Health Service will let go 1,500 employes from the agency's offices in Rockville, Prince George's Plaza in Hyattsville and the District, according to John Elsbree, director of personnel.

Sally Keeler, a spokesman for the county board of education, said 421 positions in the school system will be abolished due to budget-cutting by the school board and the County Council. Of that number, 165 are teaching jobs and the remainder are administrative and support positions.

"Right now we're saying we anticipate those people being absorbed into the system," Keeler said. "In a system as large as ours, we can always transfer people. Hopefully, we will have no employe layoffs."

John Short, director of budget and research for Montgomery, reports about 180 county positions are to be eliminated. But many of those positions, he said, are vacant, so only 50 county workers are affected. Short is confident that employes whose jobs will be cut can be kept in county government service.

For those already in search of work, the career fair on the Montgomery College campus was a gold mine of approximately 500 jobs, ranging from openings for highly skilled engineers to temporary clerical positions. Thirty representatives from county-based companies talked with applicants.

Chamber president Jim Bowman said companies paid $375 to participate in the fair, and called it a "bargain" for firms that rarely have access to several thousand job hunters in one place.

One of the most popular booths was that of Richard N. Moonblatt, owner of RNM Associates in Rockville, a job-placement agency.

Job-seekers waited as long as an hour to talk with Moonblatt, an enthusiastic counselor who seemed able to encourage even the most discouraged job hunter.

"You've got to sell yourself," Moonblatt repeated again and again in his effusive style. "I feel like this is a canned speech, but remember, don't take no for an answer. Keep pushing. Research a company before you go on an interview. Follow up the interview with a letter and then phone calls."

Moonblatt received 400 resumes at the fair, he said. As of late last week he had placed five persons in new positions and was working with another 30.

He said he was "overwhelmed" by the numbers of government workers seeking his help.

"It's killing me to tell these people to fall back on skills like typing and shorthand to find jobs," he said.

"It's hard to move on after 10 years in government service, since the government has priced many people out of the market," he continued.

But Moonblatt is convinced "there's no such thing as unemployment in Washington," a statement that elicited groans from the jobseekers gathered around his booth. "A lot of you know you have to be in the right place at the right time and have some connection, but the jobs are there."

Moonblatt admits entry-level openings outnumber those at the management level, making it even more crucial for management types to master job-hunting techniques.

"You'd be amazed at how many executives with 10 to 15 years experience wouldn't get past a personnel clerk with their interviewing techniques. They're turning people off with their unprofessional appearances, resumes and attitudes," Moonblatt said.

He emphasizes, "projecting an employable image," to capture a prospective employer's attention.