Rep. Mary Rose Oakar (D-Ohio) yesterday introduced legislation that would mandate a five-year test of alternate ways to set levels of federal pay.

The experiment would involve about 20 percent of the government's 1.2 million white-collar workers and, as proposed, also would make it tougher for the president to deny raises.

Oakar's bill incorporates some of the pay-for-performance proposals recommended earlier this week by President Reagan. But it goes further by allowing unions to bargain over wages, something they are not permitted to do now. It also proposes more varied pay experiments based on occupation, grade level, geographic location or all three.

Oakar chairs the compensation and employe benefits subcommittee of the House Post Office-Civil Service Committee. Her bill is supported by most federal unions -- which helped draft it. Hearings are scheduled to begin this month.

In making his proposals, the president called for expansion of the so-called China Lake experiment, which has allowed Navy civilian managers at two California work sites to pay employes -- mostly scientific, engineering and technical personnel -- solely on the basis of performance, without regard to regular civil service procedures.

Unions representing about 60 percent of the federal work force are wary of a governmentwide expansion of the China Lake system, which they maintain is tilted in favor of management.

Here is a rundown of Oakar's proposal, which would affect many of the 400,000 federal workers in the Washington-Baltimore area if it becomes law. It would:

*Create a 13-member federal compensation board to design, implement and evaluate a series of experimental pay programs that could be tested on upward of 250,000 workers. The board, which would consist of both federal and private pay experts, would determine which plan or plans should be applied to the entire federal work force.

*Incorporate into federal employment programs the use of pay-for-performance, collective bargaining, "total compensation" and regional pay systems.

For example, the compensation board could decide to let one agency bargain directly with workers over pay and some fringe benefits.

It also could allow pay decisions in an agency, or for a particular group of workers, to be based on performance. Bosses, rather than civil service rules and timetables, could determine the frequency and size of raises for individual workers.

"Total compensation" is a system of comparing the entire government compensation package (salary, holidays, sick leave, retirement benefits and health insurance) with pay and benefits offered workers in similar private-sector jobs. Current government pay decisions are based on pay-versus-pay surveys only.

*Reverse the system Uncle Sam now uses to determine which federal occupations are covered by a system under which some scientists, engineers and other hard-to-hire employes receive special higher salaries.

Those determinations are now made by the Office of Personnel Management. Oakar's bill would let agencies set their own salaries for special-rate personnel, subject to OPM's veto. In addition, the bill would guarantee that special-rate employes get the same percentage pay raise that goes to regular civil servants.

*Make it tougher for the president to disregard pay raises that white-collar workers are supposed to get to keep federal salaries comparable to private industry's. The president can now lower or ignore those pay raise recommendations, unless his order is overturned by the Senate and House. Oakar would guarantee employes those annual pay raises unless Congress approved a pay delay or freeze recommended by the president.