The chairman and the ranking Democrat on the Senate Foreign Relations Committee are still wondering what Ernest Lefever, President Reagan's ill-fated nominee for assistant secretary of state for human rights, will be doing as a State Department consultant. So they have asked Secretary of State Alexander M. Haig Jr. to fill them in.

Lefever, who withdrew as the nominee for the human rights job after an unfavorable committee vote, has been hired at State as a part-time consultant. In a letter dispatched last week, committee Chairman Charles H. Percy (R-Ill.) and Sen. Claiborne Pell (D-R.I.) asked Haig to tell them what Lefever's specific duties were, to whom he reports and how often. They also wanted to know if Reagan intended to fill the human rights spot. And if so, when. And if not, why not.

Meanwhile, on the other side of the Hill, members of the House Foreign Affairs Committee are circulating a letter, pushing committee member Millicent Fenwick (R-N.J.) for the rights job. Fenwick was praised for her eloquence and "deep, heartfelt conviction that all peoples should be free of tyranny." The congresswoman, however, dismissed the effort as "merely a very kindly gesture on the part of my colleagues."

Undersecretary of state Walter J. Stoessel told a Foreign Relations subcommittee the day before the date of the Percy-Pell letter that the administration still plans to fill the spot.

Or at least it seems he said that. His words were: "We are not contemplating disestablishing the office."