Dr. Donald E. Ross, 88, who encountered the wrath of organized medicine when he and the late Dr. H. Clifford Loos pioneered the prepaid health care field a half-century ago, died Monday in a Pasadena hospital. The cause of death was not reported.

Dr. Ross and Dr. Loos, who died in 1960 at 78, began their Ross-Loos Medical Group in 1929. Five years later, they were expelled by the Los Angeles County Medical Association because many doctors felt they were violating professional ethics.

They were ordered reinstated, however, when the Judicial Council of the American Medical Association investigated and found no proof of the charges.

Dr. Ross, who was born in Clinton, Ontario, attended the Unversity of Toronto Medical School and practiced in Swift Current, Saskatchewan, where he contracted to provide health care for Canadian Pacific Railroad employes under the company's medical plan.

When he moved to Southern California in 1925, Dr. Ross was in the process of buying the practice of Dr. Loos when the two decided to set up their own prepaid health plan. Their first subscribers were 400 Los Angeles Department of Water and Power employes who paid $1.50 each a month.

In 1964, when the Ross-Loos organization had grown to 140,000 subscribers and dependents, Dr. Ross said he was still convinced that low-cost, high-quality care was possible for everybody -- but he doubted the public would ever get it.

He predicted, rather, that the nation eventually would have socialized medicine and said it would cost much more than the private medical plans for which he helped set the pattern.

And although he was at odds with much of organized medicine over the latter concept, he shared its opposition to government intervention.

Dr. Ross, who was twice a widower, is survived by a son, Dr. Donald W., who practices at the Ross-Loos clinic; a daughter, Mary Park of New Orleans; a brother, Stewart Ross of Ontario, and five grandchildren.