Over the Reagan administration's objections, the House Foreign Affairs Committee voted yesterday to place Iraq back on the list of countries abetting terrorism and to revive restrictions on trade with South Africa that the administration had removed three months ago.

The double setback for the administration came as the committee completed action on a $10.8 billion foreign aid authorization--about $300 million less than the administration sought.

The bill, containing large military aid packages for Israel and Egypt and a major increase for El Salvador, was sent to the House floor with a warning from Chairman Clement J. Zablocki (D-Wis.) that it faces trouble because of the spending total and controversial amendments awaiting it from several sides. It could become "a monstrous Christmas tree and we could lose the bill," Zablocki warned.

The measure contains much of what the administration sought, particularly for Latin American governments, but it reduces amounts requested for military aid to some African countries.

An amendment passed yesterday would reverse the administration's Feb. 26 decision opening the door for trade with Iraq and South Africa of items previously forbidden under regulations established during the Carter administration.

The Reagan administration removed Iraq from the list of terrorist countries, thus permitting sales to that country, and had relaxed Export Administration Act rules to permit the sale of nonmilitary items to the South African military forces and police.

The effect of an amendment by Rep. Jonathan B. Bingham (D-N.Y.) was to roll back those changes and bar trade. It passed 17 to 11 after Republicans altered it to give the president the right to waive the restrictions if U.S. security interests are at stake.

The reversal was strongly opposed by the State Department. William Root, director of the department's Office of East-West Trade, argued that in the last few years, Iraq's support for Arab terrorist organizations had diminished. The administration wanted Iraq off the terrorist list in order to encourage it in that direction, he said.

Root later told reporters the reversal on Iraq could have a major effect on sales to Middle East countries, especially sales of U.S.-manufactured cargo aircraft, because Mideast nations may be reluctant to enter into contracts if they think that they, too, could be cut off by changes in American trade regulations. There have been reports that Iraq had intended to purchase civilian versions of military C130 cargo planes.

But several congressmen, including Benjamin A. Gilman (R-N.Y.), who usually supports the administration, cited news reports to question whether Iraq's support for international terrorism had declined. "There are still active terrorist elements operating out of Iraq, according to press accounts," Gilman told Root.

Chairman Howard Wolpe (D-Mich.) of the Africa subcommittee had sharply criticized the administration for relaxing rules on trade with South Africa, arguing that even ostensibly nonmilitary equipment could be used for military purposes and in support of racial segregation there. The amendment passed yesterday would again bar all sales of such equipment to the military and police of that country.

The bill brings the total foreign aid authorization for fiscal 1983 to $10.8 billion in direct military and economic aid and guaranteed loans; although the sum is close to the $11.1 billion requested by the administration, the measure parcels it out in a manner different from what the administration sought.

The committee voted $539 million less in direct military sales credits than the administration wanted for a number of countries and divided that amount for most between military assistance programs and guaranteed loans. The guaranteed loans are off-budget items and make the spending total appear to be less. They are also less attractive to recipient countries than are the direct credits sought by the administration.

The committee reduced from $100 million to $50 million the amount of military aid intended for Morocco.

Israel wound up with $1.7 billion in military aid for fiscal 1983, and Egypt $1.3 billion. They are the largest beneficiaries of the measure.