THE NEW MIDDLE EAST report of Sens. Abraham Rubicoff (D-Conn.) and Howard Baker (R-Tenn.), who led a delegation of 12 senators on a study mission in November, provides reassuring evidence of the quantity and quality of congressional involvement in dealing with the problems of that troubled region. Just since the 1973 war, perhaps 200 legislators have visited the Mideast; there is no comparable record of first-hand congressional familiarization with both sides of any other regional dispute in which the United States has an interest. This has given the Congress a fair claim to be included as a responsible partner in Amrican Mideast policy-making. We would not say Congress has always been wise in its approach to the Mideast, nor has the executive (Who has for the matter?). But by and large, the congressional challenge to the policy-makers downtown has been increasingly subordinated to the requirement for national cooperation. The Ribicoff-Baker report is a cse in point.

The report is, if you will, even handded: Its premise is that the United States needs the confidence of Arabs as well as Israelis to serve its own interests and theirs. It acknowledges both the political complexity and the emotional/psycological twist of the issues dividing the parties. It notes indications that Arabs "moderates" are ready to accept the existence of Israel as a sovereign Jewish state. It considers ways in which the Palestanians could be brought into negotiations. Finally, it accepts that American leadership is essential if the region is to move toward peace. If these points seen unexceptionable, then that is a telling comment in itself on how far congressional (and public) opinion has moved in recent years. It was not so very long ago that none of these considerations was widely granted.

Sensibly, the Ribicoff-Baker report does not attmpt to lay dowm specific guidelines for a settlement. In its general observations, however, it takes an independent-minded tack taht is likely to give some satisfaction, and some offense, to both sides. It calls for negotiated borders that are, from Israel's viewpoint, "militarily defensible." It sems to sympathize with the Arab desire to substitute American guarantees of Israel for direct Arab ties with Israel.One can argue these and other pointsM but that is not what is important. The administration is taking its time on the Mideast, as it should. The substance is had; the local political timetables, particularly Israel's elections in May, can, be deplored byt not ignored. Secretary of State Vance's reconnaissance trip, which is to start on Monday, is a good way to start. The report by Sens. Baker and Ribicoff indicates that when the administration is finally ready, the Congress will be, too.