President Reagan's once-proud "kitchen cabinet" -- that collection of trusted millionaires who gave generously of their money and advice -- has fallen upon hard times.

First, their feelings were ruffled when they were evicted from the Executive Office Building. Then, some of them were told to disband the Coalition for a New Beginning, which was supposed to sell the Reagan economic program to the country.

Yesterday, the long-simmering private feelings of some kitchen cabinet members boiled openly when Justin Dart, one of the group's founders, told Jack Nelson of the Los Angeles Times that the group had outlived its usefulness.

"The kitchen cabinet has served its useful purpose, and unless the president calls on some of us, the cabinet is finished," said Dart, a Los Angeles industrialist. "It hasn't any reason to survive."

Another prominent kitchen cabinet member, who asked not to be quoted by name, said Dart was "just blowing off steam" and that the group will not disband. But he acknowledged that many kitchen cabinet members share Dart's anger at reports that corporations were pressured into giving money to the ill-fated Coalition for a New Beginning.

Dart denies there were any such heavy-handed tactics But there were enough reports to this effect that high White House aides became uneasy and suggested that the group disband.

Since the kitchen cabinet members are overwhelmingly loyal to Reagan and were stung by the suggestion that they were damaging him politically, the suggestion was equivalent to a command. The coalition closed its doors and Dart, left in charge when Charles Wick became head of the International Communication Agency, announced that the $800,000 that had been collected would be refunded. But some of the kitchen cabinet members, who have been raising money for Reagan since he first ran for office in 1966, felt they had been treated shabbily.

In trying to help Reagan as president, the kitchen cabinet's lack of existence as a formal entity worked against it. Some of its members were organized into a personnel group with the avowed aim of placing Reagan loyalists in federal jobs, and it was this section of the cabinet that was housed in the Executive Office Building near the office of its ally, White House political adviser Lyn Nofziger.

Another overlapping group of kitchen cabinet members put together the coalition, which had its offices outside the White House.

But in the perception of much of the press and the public, these two groups were indistinguishable, and it appeared that the administration was trying to mobilize public opinion with a fund-raising campaign directed from the White House.

"The people running the coalition were just too close to the president," said one person who was involved in the fund-raising operation. "It was a mistake to begin with."

When the kitchen cabinet's personnel group was evicted from the Executive Office Building, the White House explanation was that the space was needed for other purposes. In fact, White House chief of staff James A. Baker III and counselor Edwin Meese III had obtained a legal opinion that the kitchen cabinet members would be subject to federal disclosure and conflict-of-interest laws if they stayed on longer than 60 days.

It might be said that success also has spoiled the kitchen cabinet. William French Smith, who headed the original personnel operation, became attorney general. William Wilson, who took over for Smith, was appointed special liaison to the Vatican. Wick was named to the ICA. Theodore Cummings, another millionaire supporter, was picked for ambassador to Austria.

Others in the kitchen cabinet also are reportedly in line for top jobs if they want them. Alfred Bloomingdale, one of the most socially prominent and richest members of the group, supposedly will become ambassador to France.

Age and illness has overtaken others in the group. But Reagan has a habit of going back to those who were with him in the beginning, and it is unlikely that he will stop relying on his millionaire advisers.

"They are a candid, knowledgeable sounding board," said Sen. Paul Laxalt (R-Nev.), the only elected officeholder who is a member. "I'm sure the president is going to continue to count upon them as a continuing, active force."