Ambassador Robert S. Strauss, beaming with pleasure, took time out from his new Mideast assignment yesterday to praise the overwhelming 395-7 House approval of the new international trade treaty he had negotiated.

"I feel tremendous," Strauss said in his Office of the Special Trade Representative - now strewn with large maps of the Middle East. "That is a legislative accomplishment for this Administration."

The House vote gives approval to a package of agreements, which - when ratified by the Senate - will cut tariffs aboout 30 per cent over eight years, and install a number of codes of behavior covering non-tariff barriers.

Whilecrediting "the solid course set by President Carter," and bi-partisan cooperation on Capitol Hill for the victory in the House, Strauss made it plain he took the trade success as a good augury for his new negotiating role in the Middle East.

When he first took over the role as Special Trade Representative - a responsibility for which many critics said he was ill-qualified - Strauss said he found that it took 60 to 70 days to get Congress an answer from the bureaucracy. In short order, Strauss got the average response time down to 7 days.

"I went back and looked at the old clips - quote me - I went and looked at the old clips when Carter appointed me to this job, and the clips when he appointed me to the Middle East job, and a lot of the same son-of-a-bitches are saying the same things now they said then. That's why I'm enjoying this 395-7 vote, for a darn good trade package in the best interest of this county."

Strauss returned Sunday from a week-long tour of the Middle East with renewed hopes for breaking the logjam on negotiations over the Palestinian question.

Strauss is patterning much of his Middle East strategy on the give-and-take methods he used in getting the trade bill this far in Congress.

While Strauss is now preoccupied with his new venture into diplomacy, he took the time yesterday to bask a bit in the glory of the House trade bill vote and to strengthen the lines of support he will need in the Senate.

Welcoming Japanese Ambassador Togo into his office, Strauss said: "Mr. Ambassador, did you see that vote? We lost seven of 'em, and I'm looking up right now to see who they are."

Strauss conceded that a favorable vote in the Senate is not likely to be as heavy as in the House, and admitted that "if we don't get the Senate satisfied on trade reorganization, we won't even get the bill out of the Finance Committee." He nonetheless predicted eventual success.

Strauss intends to present the Administration's trade reorganization proposals within the next two weeks - or well after the promised date of July 10, a delay resulting from Presidential concentration on energy and economic matters at Camp David.

Key Senators, led by Abraham Ribicoff (D-Conn.) and William V. Roth, Jr. (R-Del.) have co-sponsored a bill to consolidtate the government's trade functions and policy-making into a single department.

President Carter has all but ruled out a new department, but Strauss said in the interview that the President could probably meet Ribicoff's and Roth's main objectives. One of their main goals is to move the countervailing duty function out of the Treasury.

Although Carter has not yet "signed off" on the Administration's reorganization proposals, Strauss - over Treasury Secretary Blumenthal's objections - indicated that the Treasury functions probably would be moved into a strengthened STR office. Additional functions relating to export promotion might be assigned to the Commerce Department.

On another subject, Strauss said that the Saudi Arabian government's decision to add, at least temporarily, 1 million barrels of oil production a day was in part a favorable response to the Tokyo summit's decision to put a lid on oil imports. Strauss said he knows that Crown Prince Fahd desires to demonstrate that the Saudis "are a more moderate and responsible supplier" than other Middle Eastern oil producers. CAPTION: Picture, ROBERT S. STRAUSS . . . "a legislative accomplishment"