For years, one of the favorite pastimes of Congress-watchers here has been waiting to see when the Senate Finance Committee would outdo itself. Only the Finance Committee can dole out outrageous tax breaks with so much style and panache. The House Ways and Means Committee just doesn't have the flair.

For as long as most observers here can remember, the Finance Committee has been an easy target for groups seeking special writeoffs. Big Oil, high-income investors, housing speculators -- virtually no one who entered the committee's back rooms ever would be turned down.

Well, this week the long-awaited moment arrived when the panel managed (during its debate on the president's "windfall profits" tax to give away more money in tax breaks than the windfall levy would raise -- marking the first time in memory that a congressional committee has run up its own deficit.

By late yesterday the committee actually had amassed a red-ink figure of $20.6 billion -- outstripping even the Carter administration, which has amassed only a $45 billion deficit this year on the entire federal budget. Moreover, the Finance Committee did it in only six days. Carter has taken 11 months.

What dismayed some observers here was not so much the predicament, which may be funny, up to a point, but how blithely the panel members put themselves into it without any real thought of what it meant in terms of fiscal discipline. Everyone's pet project was voted in, no matter what the cost.

The committee began ostensibly to work on the House version of Carter's proposal, imposing what everyone agreed was a mild excise tax on some categories of oil. The measure, only slightly stiffer than the president's, would have brought in $104 billion in new revenues over a period of 10 years.

Before even starting on the tax portion of the bill, however, committee members began a stampede to push through their own individual proposals for tax credits, eventually running the total up to $99.2 billion. At the same time, they also trimmed the tax bite of the House bill by $25.4 billion.

Most frustrating to some onlookers, the changes were pushed through with virtually no pause for thought about their cost or actual impact. "It was just like a bunch of college kids drinking beer," mused one observer. "It didn't matter how much they'd drunk before. They just chug-a-lugged it all."

Item: The committee early on defeated a dubious plan for an oil shale tax credit, in part because of lack of interest in the measure. So, what did proponents do? The expanded it to cover other synthetic fuels as well -- at several times the cost. The proposal passed by unanimous vote.

Item: A sweeping proposal by Sen. Robert Packwood (R-Ore.) for a massive $75 billion in energy tax credits was deemed too big to consider all in one day. So, the panel members proceeded cautiously: They approved it over four days -- with almost no real debate.

Item: The committee unhesitatingly gave the nod to a costly proposal that would provide a tax credit to homeowners for the purchase of new furnaces. Members brushed aside Treasury protests that they also were spending government money on buyers who would have had to replace their old furnaces anyway.

Item: A 1977 tax credit for installation of home insulation created such a shortage of materials that it sent retail prices soaring and encouraged the use of inferior substitutes. No matter, said its sponsors. The panel voted to increase the credit anyway.

As if the tax giveaway weren't reckless enough, panel members virtually tripped over each other later to exempt more and more categories of oil from the windfall tax, thus decreasing the amount of new revenues from the measure that could be made available to finance their new tax-credit proposals.

The long-pang of conscience came from Sen. John Chafee (R-R.I.) -- but for the wrong reasons: Chafee pleaded firmly enough for more fiscal discipline. But his plea was based on fears that there wouldn't be enough left for his own tax-credit proposal.

What troubled some observers was the shamelessness with which the committee embarked on its spree. Most of the proposals were obvious political gimmicks, designed to win points with specific constituent groups. Yet warnings about the consequences were ignored. Dubious "studies" were cited without challenge.

Admittedly, at least some of the panel's past week's performance stems from the widely-chronicled clubbiness of the Senate, which finds many senators supporting provisions they otherwise might vote down just to "accommodate" their colleagues. You vote for my proposal and I'll vote for yours.

Indeed, Long's success as a tactician has been based largely on acquiescing to this during the debate and then scrapping some of the more objectionable provisions during a House-Senate conference on a measure. In one sense, that may be the only way to impose any discipline on the Senate. Sometimes it works.

But this time, the consensus is that the Finance Committee has outdone even itself by carrying the "be-one-of-the-boys" game too far, close to what some observers consider plain irresponsibility. Even if the panel pares back its tax credits, as Long is planning, it can't really restore a very viable tax.

It may be, as some senators have contended, that the country would be better off without a windfall profits tax than with one, or that providing massive tax credits for development of new energy sources is a better solution to the nation's problems than Carter's proposed synthetic fuels plan.

The presient's proposals have been wiely criticized by responsible energy economists. The windfall tax -- so weak that it isn't being challenged by the major oil companies -- has been dismissed as a political gesture. And even without a windfall tax, the oil firms will have to pay income taxes on profits.

But there are those who argue as well that if Finance Committee members wanted to vote down the windfall tax and replace Carter's synthetic fuels program with a series of tax credits, they should have done it squarely and with some integrity, and not in the rush of an undisciplined spree.