Last week Ronald Volk visited three southern college campuses to recruit engineers and other skilled workers for the nation's largest employer, the federal government.

As a civilian personnel officer for the Department of the Army, Volk is part of the federal government's constant search for new talent, a search that is still under way despite President Reagan's much publicized freeze on federal hiring.

Although there is no evidence that anyone has directly defied the order by authorizing new hires, various agencies -- apparently acting on the belief that the freeze eventually will be lifted -- have listed more than 800 new job openings since Jan. 24, four days after the freeze was announced, bringing the total number of advertised openings to 3,100. Before the Jan. 20 announcement, there was an average of 3,500 job openings on any day in the federal civilian work force.

Oblivious to Executive Order No. 1 of the Reagan administration, recruiters from a number of agencies are on the road this week, telling high school and college students from coast-to-coast the benefits of working for the federal government: Good salaries (from $7,960 a year for entry-level Gs-1 to $50,112 for Gs-15, Step 5 and up), liberal pension and benefit plans and -- presidential cutback plans not withstanding -- job security.

At the Defense Department, home to about half of the 2.8 million civilian employes of the government, it's business as usual, according to one source.

Interviews on college campuses are scheduled as much as a year in advance, so recruiters are keeping those dates, on the assumption that the freeze won't go on forever, and that in the meantime, the Pentagon, which has been promised additional funds by the Reagan administration, can count on getting a large number of exemptions.

One place where the interviewing has stopped is the Department of Agriculture. John W. Fossum, director of personnel, said it would be "inappropriate" to seek new workers in the face of the freeze. "It also would be difficult to recruit when we don't know what the new personnel ceilings will be," Fossum said.

Fossum said that until the freeze is lifted, hiring at Agriculture would be limited to transfers within the department.

The Department of Energy, targeted for major cutbacks in the new administration, also has put its recruiters on hold, a spokesman said yestereday.

For Volk, who is based in Atlanta, the freeze is "just another problem." He said that in fields such as engineering, the big drawback to federal employment is money.Starting government salaries for graduating engineers range from $15,947 to $19,747, depending on academic performance and the area of specialization. At best, that is about $3,000 a year below offers from private industry, Volk said.

The hiring freeze "caused a few cancellations" by students who are chary of staking their future on a job that may not materialize. But for the most part, college seniors showed up on schedule last week when Volk visited Tulane, Louisiana Tech and Prairie View A & M.

A personnel officer at the main Defense recruiting office at the Pentagon said a significant number of college seniors in the East, where impact of the freeze has been most widely publicized, canceled appointments.

"The recruiter who was scheduled to go to Villanova [in suburban Philadelphia] was wiped out," the official said. But most recruiters who visited the traditional sources of federal hiring, big state universities and certain small private Southern Schools, got responses similar to Wick, the official said.

An offical at the Office of Management and Budget, which is charged with enforcing the freeze, said continued recruiting could reflect "the lag time in filtering the word through the huge federal establishment," which includes between 1,000 and 2,000 personnel officers, and "an amount of optimism that at some time in the future the freeze will be lifted and the positions will be filled."

When asked whether the continued recruiting troubled him, the OMB official responded: "I can't say it [the recruiting] shouldn't occur, unless it is overdone."

OMB has received very few requests for exemptions to the freeze based on immediate need, the easiest way to get around the freeze.

The official added that because of lawsuits, OMB's general counsel had advised him not to comment on the status of appeals brought on behalf of individuals hired between Nov. 5 (the day after the election) and Jan. 20 who had not begun work by the time the freeze was announced. The first court test of the freeze last Friday, resulted in a setback for the administration when a judge ordered two individuals reinstated.

As of yesterday for example, the Energy Department had received 65 appeals based on hardship.

Judy A. German, owner-operator of Federal Research Service, one of several private organizations which compile lists of federal job openings and then sell newsletters to job hunters, said she is "seeing some caution" in listings by the various agencies. But she believes most personnel officers are continuing to recruit prospective employes because it takes about three months to process an application and because they are guessing that the freeze will last three to six months.

For clients who subscribe to her service, German offers this encouraging advice: "Historically, federal job freezes do not work." Since World War II, she said, there have been only two periods without any kind of hiring controls, two years in the Eisenhower administration and nine months under President Johnson. Yet federal employment continued to grow. "Over the past 35 years, the bureaucracy has leaned the 'tricks of the trade' needed to effectively work around hiring controls. There is no reason to believe that circumstances will be any different under the current hiring freeze."