Key members of the House Education and Labor Committee endorsed compromise legislation yesterday to guarantee employes in firms with 50 or more employes unpaid leave to care for new babies, sick children or elderly parents.

The bill would require the employer to continue health benefits during the leave and to guarantee the employe the same or equivalent job upon returning to work.

Rep. Augustus F. Hawkins (D-Calif.), the committee chairman, scheduled committee consideration of the measure for Tuesday and said in a statement that the measure would provide "minimum job protections for American workers . . . at a reasonable cost."

The compromise differs from an earlier version by exempting all businesses with fewer than 50 employes, an estimated 95 percent of the country's employers. The original bill, and a similar measure proposed in the Senate, applied to all businesses with at least 15 employes.

The Reagan administration has opposed parental leave legislation, saying that fringe benefits should be negotiated between workers and employers -- not mandated by the government. Business groups have opposed the legislation, arguing that it would cost employers too much and might lead to more federally mandated employe benefits.

The compromise proposal would enable an eligible employe to take up to 10 weeks of unpaid leave to care for a newborn, a newly adopted baby or a seriously ill child or parent. Up to 15 weeks of unpaid leave could be taken for the employe's own serious illness.

"If you look at American families, they are in as much trouble as the stock market . . . . All we have given them is rhetoric," Rep. Patricia Schroeder (D-Colo.) said at a news conference at which she endorsed the compromise. Schroeder wrote the earlier bill.

The House sponsors took heart from a General Accounting Office study released yesterday projecting that the compromise would cost the employers $188 million a year, far less than estimated by business groups opposing the bill, and would benefit up to 1.7 million people.

However, they could not say how many of the 1.7 million already may be eligible for unpaid leave under their employers' policies.

Rep. Marge Roukema (R-N.J.), ranking minority member of the subcommittee on labor-management relations and a sponsor of the compromise, said she wanted to "dispel the idea that this is a 'yuppie woman's bill.' " She said that it would help those less able to care for themselves and more likely to work for employers without such "enlightened" leave policies.

Roukema said sponsors are aiming for full House action late this year or early next year.

The GAO estimated that a Senate parental leave bill, which does not include elderly care but applies to more businesses, would cost employers about $500 million a year.

The National Federation of Independent Business, representing smaller businesses, calling the GAO's estimates "seriously flawed," said the bill would "eliminate jobs, bankrupt companies and in the long run ensure the downhill slide of our national competitiveness."