Sometime before America celebrates its 205th birthday next month, the House and Senate will complete action on legislation that a growing number of members are coming to regard as historically important, and perhaps historically dangerous, depending on whom you ask.

The legislation involves cutting the budget, but it could affect much more than the level of federal spending next year. Depending on how members vote in the weeks ahead, they could set off an enormous shift of power in the government, transferring influence from the traditional congressional committees that have long dominated this town to the relatively new House and Senate Budget committees and the Office of Management and Budget in the White House.

At stake, according to Chairman Richard Bolling (D-Mo.) of the House Rules Committee, is "the viability of the Congress as an element of government." Bolling's language is strong, but his concern is widely shared, particularly among senior House Democrats.

The legislation in question is the package of "reconciliation" measures that are now required under the budget act to bring all government spending in line with spending limits already adopted by both houses.

In ways that members of Congress are just beginning to appreciate, the reconciliation procedure can be used to rewrite laws, wiping out or fundamentally changing government programs.

The Reagan administration fully appreciates the revolutionary potential of this legislation, and is assigning it the highest priority.

The White House staff and the career civil servants at the OMB have been fully mobilized to help guide these bills through the House and Senate.

OMB Director David A. Stockman apparently sees a chance to impose a kind of political discipline on Congress that is traditionally associated with a European parliamentary system, not the unwieldy American form of representative government.

That prospect alarms some members of Congress, predictably including some Democrats who are not enthusiastic supporters of the Reagan budget. "It's an extremely dangerous situation," said Rep. Gillis W. Long (D-La.), one of the original managers of the 1974 budget bill that created the procedure Congress is now using.

At the same time, some members see the procedure as an opportunity for House committees to protect their favorite programs, one that might be in danger in the prevailing political climate.

This is potentially possible because the reconciliation bill will go to the House floor under legislative conditions that will make it impossilbe to offer very many amendments. Some sections -- the Banking Committee's rewrite of some basic housing legislation, for example -- will be effectively insulated from changes on the floor.

What most worries members like Bolling and Long, though, is the prospect of a Republican-sponsored "substitute" for the reconciliation program that the House committees will produce, a substitute that could ignore some or all of the committees' decisions.

Under the budget procedure, each committee is entitled to make its own recommendations about how to meet the spending ceilings in its area of responsibility. So, for example, the Education and Labor Committee can jigger its beloved social programs as it sees fit.

This at least preserves the traditional committee functions. But if Republicans and conservative Democrats throw out the committees' recommendations in favor of a White House-backed substitute, that bill could end up rewriting basic programs without even consulting the committees that created them.

This, Bolling said, would be "an excessive attempt to do everything in one resolution" that could end up destroying the budget procedures.

There is no concensus in Congress about the new state of affairs except that it really is new, and surprising. "It has been a very surprising thing that the House has been wiling to work so hard on reconciliation," said Rep. Bill Frenzel (R-Minn.). "Things changed very quickly around here," said Frenzel, a supporter of the Reagan economic program. "It's just been delightful."

"It's really been a surprise," agreed Rep. Morris K. Udall (D-Ariz.)., who sees it from a liberal perspective. "It's an illustration of Udall's Fourth Law," he added: "Any change or reform you make is going to have consequences you don't like."

Udall was referring to the fact that he and many other liberal Democrats were ardent promoters of the budget reform procedures that have made the current situation possible.

They backed it as a way to give Congress an equal say with the executive branch in the budget process. Many Republicans, particularly in the House, who now embrace the new procedures opposed them for years.

This year a shrewd new budget director -- a former member of the House who understands the possibilities inherent in the budget act -- created a new kind of game on Capitol Hill. Stockman is no mere technician.As he demonstrated in his years in Congress, he is a deeply ideological conservative who is eager to dismantely many of the government programs set up in the '60s and '70s.

There is no indication that Stockman would mind at all if Congress decides with one vote during this warm season of continuing honeymoon for President Reagan to adopt his vision of a significantly altered federal government. As many members pointed out in interviews, there is no way to deny Congress this chance to "work its will."

From his country home in Connecticut, one of the original authors of the budget process, former senator Abraham A. Ribicoff, a Democrat, made this indisputable observation: "The way the budget process is working this year is how it was intended to work when the legislation was passed."