It all began with one of those Washington do-gooder workshops.

Forty-seven Roman Catholic sisters from all over the country had responded to an invitation to come for a weekend and talk about how the growing mood of activism among religious women in 1971 could be mobilized to influence social policy.

Out of that weekend of crash courses on politics, discussion and prayer emerged the determination by the nuns to establish a political action network of information and communication, subsequently shortened to just NETWORK.

On Wednesday night NETWORK celebrated its 15th anniversary as "the first registered Catholic social justice lobby" with a party at which a number of awards were handed out.

The Philip A. Hart awards, named for the late Michigan senator, were presented to six congresswomen. "The beginning of a Congressional Sodality," joked Rep. Barbara Mikulski (D-Md.), one of the honorees.

While the mood of the evening was celebration, it was the congresswomen who reminded the several hundred boosters present of the more serious business that underlay the event.

"The most important time is the next 90 days," said Rep. Barbara Kennelly (D-Conn.), just returned from a congressional tour of Central America where, she said, "we talked to everybody."

"The contras can't do it; they're part of the problem," she said. And in a plea for grass-roots support to help defeat the Reagan administration's bill to aid the Nicaraguan rebels, she pleaded, "Just try a little harder for the next 90 days."

From the other side of the aisle but the same side of the Nicaragua issue, Rep. Claudine Schneider (R-R.I.) said, "One of my blackest weeks was the week we voted on Nicaragua." She too pleaded that "each and every one of you please do more."

In accepting her award, Rep. Marcy Kaptur (D-Ohio), praised the group that gave it to her. "I think your newsletter is the best resource that I have on so many issues," she said of NETWORK's bi-monthly publication.

Other recipients of the Hart award were Rep. Lindy Boggs (D-La.) and Rep. Mary Rose Oakar (D-Ohio).

Special service awards also were given to Thomas E. Quigley, adviser on Latin American affairs for the United States Catholic Conference, and to Sister Kate McDonnell, pioneer in housing for the poor and executive director of Housing Counseling Services Inc.

From the 47 nuns who founded NETWORK, the organization has grown to a current membership of more than 8,000 across the country, said Sister Dorothy Vidulich, one of 10 staff members in the Washington office. Members are men and women, lay and clergy, Catholic and non-Catholic, she said, though nuns probably remain the largest single group.

An annual legislative seminar, usually held in June by NETWORK, brings about 125 persons here for both briefing and hands-on experience at lobbying.

Over the years, NETWORK has dealt with a host of issues, from welfare reform to the Law of the Sea, from the Panama Canal treaty to Gramm-Rudman budget cuts. They leave the more traditionally Catholic issues, such as abortion and aid to parochial schools, to more traditional Catholic agencies.

The common denominator is "a primary focus on how U.S. policy affects the economically poor," says a NETWORK brochure.

Priority issues currently, said Vidulich, include South Africa, Central America and Contra aid, military spending and budget cuts.

With unpaid coordinators in every state and most congressional districts, and with a religiously dedicated following, the 8,000 members can be effective far beyond their numbers in generating political presssure, said lobbyist Catherine Brousseau.

On issues such as contra aid, Brousseau said, "Our members are all so well informed that many of them have their own sources." And if NETWORK members visit Central America and come back with firsthand accounts that could be helpful, "we try to get those stories up to the Hill," she said.