They wore "Senior Power" buttons and talked anxiously about inflation and soaring medical care costs over their coffee and danishes -- a typical morning for 225 Congressional Senior Citizen Interns.

By the end of their 12-hour day, interns like Ernie Greenwald of Silver Spring and Cora Wood of Colmar Manor had confronted legislators and bureaucrats with tough questions on issues as diverse as physical fitness and Social Security benefits.

"The issue is that so many [senior citizens] are on a fixed income and inflation is wiping them out," said Greenwald, a retired federal employe and an intern in the office of Democratic Rep. Michael D. Barnes of Maryland's 8th Congressional District. "They are taxed on their income, and everything costs more. Everything follows from that."

Last week marked the eighth year of the Congressional Senior Citizen Intern Program, a two-week visit to Capitol Hill by senior citizens from across the country.This year, 150 U.S. representatives chose persons from their districts to work in their offices and to hear briefings on the problems of the elderly.

Greenwald, an active member of Jewish Community Center Senior Adult Club in Rockville, is reluctant to refer to himself as a senior citizen. He is 58.

"I'm seeing this as a retiree, not exactly a senior citizen," he said. "The government promised me I would have cost of living adjustments twice a year. I read today that the Congress is recommending it be reduced to once a year . . . I have recourse to nothing. All I can do is write my senator or congressman."

Fifth District Democratic Congresswoman Gladys Noon Spellman's intern, Cora Wood, considers herself a "young older American" who thinks nothing of making the one-mile walk to nearby Bladensburg. At 79, Wood recites with pride the accomplishments of her six years with Betterment for United Seniors, one of the most active senior citizens' groups in the state.

"We have to work for those who are not physically able," said Wood, who retired from teaching in Prince George's County schools after 15 years. "I will compile a list of organizations for the elderly so they will understand the advantages of being a member."

Like Greenwald, Wood considers inflation to be the biggest problem for the elderly. She is also greatly concerned about the lack of housing for the elderly and the quality of health care.

"Every project for the elderly in Prince George's County -- there's about six -- all have long waiting lists," she said.

"Many of our people are concerned about what Medicare does and doesn't do. Medicare pays 80 percent of most expenses of those over 65, but if you have an eye examination and glasses or a hearing problem that requires a hearing aid, you must pay."

A firm believer in the legislative process, Wood said she intends to alert senior citizens to how they can influence legislation by knowing the appropriate committee chairman and keeping abreast of bills affecting the elderly.

Greenwald, who considers himself a "flag waver," said he too will report to community groups on what he has learned on Capitol Hill.

"I've already been asked by two or three groups to talk on what I've heard, things to look for, things to avoid," he said.

Among these is how to prevent "ripoffs" of unsuspecting senior citizens. He said, for example, one intern from Minnesota was "fleeced" of her savings when someone representing himself as a bank representative stole her savings.

"There was a lot of, 'Yes, yes. I've heard of this happening,' or 'Tsk tsk.' I took notes furiously about what people should be on the lookout for."

Greenwald is reluctant to criticize the program. Last week's trip to the White House, however, proved to be a disappointment when Rosalynn Carter failed to make a scheduled appearence in the Rose Garden.

[The interns] thought that either the president or Mrs. Carter could have said hello. But it was drizzling that day," Greenwald said.

Wood and Greenwald seem optimistic about the results of the intern program, despite its flaws. Greenwald expressed disappointment about the caliber of speakers, many of whom were federal employes like himself. Wood said the program also lacked speakers on government's role in protection of the elderly against street crime.

Says Wood: "I'm not disillusioned at all. I think the program, if it continues, is one of the best ways to get information to people from all over the country on what [the government] is doing. And I feel that is important.

"Remember, we're not only working for the senior citizen, we're working for you, too."