REP. ROBERT E. BAUMAN (R-Md.), the self-appointed watchdog of the House, barked at a useful time last week when he blocked the Democratic leadership's attempt to reconstitute the Select Committee on Assassinations without a roll-call vote or real debate. By forcing the matter to be postponed at least until today, Rep. Bauman gave his colleagues a bit more time to think about how the House should proceed with its inquiry into the murders of President Kennedy and Martin Luther King Jr.

The issue that has caused the most public and congressional stir is the astoundin g $6.5-million one-year budget drawn up by the panel's chief counsel, former Philadelphia prosecutor Richard A. Sprague. Mr. Sprague asserts that a staff of 170, including 80 investigators, will be needed for two years to pursue all of the unresolved questions about the two assassinations and the performance of the FBI, the CIA and other agencies involved. He may be right. Yet no amount of investigating can put all the rumors to rest or still all of the unofficial sleuths who have advanced various conspiracy theories about one or both of the tragedies. Thus the House panel's goals should be more purposeful and pointed - with a budget and staff to match.

The committee's methods deserve equally careful scrutiny. Mr. Sprague originally planned to employ hidden recording devices and polygraphs and to subject witnesses' testimony to psychological stress evaluation. Those ideas may have been blocked by alert legislators such as Rep. Don Edwards (D-Calif.), who warned the House leadership that such techniques would be "wrong, immoral and very likely illegal." Yet the incident does reinforce impressions that Mr. Sprague may be inclined to operate in a free-wheeling way without enough regard for individuals rights.

Rep. Henry B. Gonzalez (D-Texas), whom Speaker Thomas P. O'Neill Jr. has designated to lead the inquiry, seems fairly sensitive to these problems. It is too soon to tell, however, whether he is capable of giving direction to the hard-charging Mr. Sprague. The leadership thus should be sure that the need to conduct these investigations in the most scrupolous and productive way. The best way to drive the point home might be to give the assassinations panel only a short-term authorization and a limited budget this week - and make clear that future support depends on how responsibly it proceeds.