President Reagan is considering more than 150 bills passed in the final days of the 98th Congress, including several that, in another season, would be likely candidates for veto.

But some also are favorites of powerful interest groups, leaving the president with some hard choices with the election so near.

A leading example grants an estimated $400 million to $800 million in relief to timber companies, mainly in the Pacific Northwest, by excusing them from old contracts to buy federal timber at what today seem high prices.

Reagan signed it yesterday.

David A. Stockman, director of the Office of Management and Budget, fought the bill when it was in the House Oct. 1, calling it "special relief" for a "small number of corporations." Some congressional sages were betting incorrectly that the president would allow the bill to die without his signature, a move known as a pocket veto.

But a veto might have had unpleasant political repercussions in Oregon and Washington, where the president's lead over Walter F. Mondale is not as large as in some other states. In addition, the bill's chief sponsor is Sen. Mark O. Hatfield (R-Ore.), who is up for reelection.

Another bill, over which some in the White House have lesser misgivings, is one that would extend Head Start and several other established programs, including the one that helps low-income families pay fuel bills.

It also would create a new program to use schools after hours to care for "latchkey children."

The White House does not object to extending Head Start, one of the most popular programs in government. But some officials are unhappy with the latchkey provision, plus a string of smaller amendments adding things such as a cancer screening clinic for southern Utah, pushed by Sen. Orrin G. Hatch (R-Utah) and a center for excellence in education at Indiana University favored by Sen. Dan Quayle (R-Ind.).

Other bills on which the president must decide in the next few weeks involve such fields as health and wilderness, taxes, trade, public broadcasting, cable television and education. He has 10 days from receipt of a bill to sign or allow it to die.

A dozen are said to be under close study. They include bills that would: Create a new American Conservation Corps, similar to the Civilian Conservation Corps of the 1930s, which would put thousands of unemployed youths to work on public lands. The administration likes neither the concept nor the $225 million, three-year price tag. Authorize a $2.9 billion, three-year investment in health manpower, which is more than the administration wants to spend and would continue some programs it wants to alter or wind down. Provide $4.7 billion for the National Institutes of Health -- the administration asked for $3.9 billion -- while creating two new institutes, on arthritis and nursing, that the administration did not want. The bill also contains disputed provisions on animal research. Authorize $368 million over four years for Indian health services.

Also at issue is a catchall reauthorization bill providing $1.2 billion this fiscal year and more in the future for 10 education programs. Again, cost is one issue.

So is the fact that the bill would continue such programs as impact aid that the administration wanted altered or phased down. The National Education Association and other education groups held a news conference yesterday to put pressure on Reagan to sign the measure.

A bill authorizing $839 million over five years for aid to libraries also is a veto possibility; the White House wanted to end the program. Another bill provides $675 million from fiscal 1987 through 1989, more than the White House wanted, for public broadcasting.

Other veto possibilities were said yesterday to be a vocational education authorization, the bill raising Medicare fees for hospices and an authorization bill for the National Oceanic and Atmospheric Administration.