The House brushed aside a veto threat yesterday and approved an $11.2 billion transportation appropriations bill that the White House says -- and congressional experts deny -- is a budget buster.

It was the third of Congress' regular 13 appropriations bills to pass the House and the first to elicit a veto threat from President Reagan's senior advisers, who let it be known earlier in the day that they could not recommend to the president that he sign the bill in its present form.

The vote to send the bill to the Senate was 268 to 119, which is more than the two-thirds required to override a veto. But a Republican-sponsored effort to help meet administration objections by cutting $320 million from rail and mass transit programs was defeated by a closer vote of 221 to 154, casting doubt on the outcome if a veto is cast.

Although Democrats contend that the bill is within the congressional budget, the administration says it exceeds that limit by $525 million, largely because some necessary funding for the Federal Aviation Administration and other agencies has been put off until later in the year, according to an Office of Management and Budget spokesman.

The House later voted, 264 to 105, to approve a $25.3 billion agriculture appropriations bill, which the administration also opposed as too costly but has not threatened to veto.

Conservatives were defeated in an effort to reduce food-stamp spending by requiring that proposed spending of $9.5 billion for the program be stretched out over the full fiscal year rather than lasting only until July 15, when a supplemental appropriation presumably would be required.

The transportation bill was approved as the House Rules Committee cleared the way for House consideration today of a huge stopgap "continuing resolution" to fund all agencies for which Congress has not approved appropriations bills by Oct. 1. This could include the entire government.

Under the terms of debate set by the Rules Committee, the resolution will for the most part not be open to amendment. Some members had asked that they be allowed, among other things, to vote to end funding for the Clinch River breeder reactor. Funds for the reactor and other controversial projects were approved in a public works appropriations bill that was sent to the floor earlier in the day by the House Appropriations Committee.

Republicans, however, will be allowed a vote to move up the proposed Feb. 18 termination date for the stopgap funding in line with Reagan's request for a shorter period and a lame-duck session after the November elections to finish action on appropriations bills.

The resolution provides generally for funding at current levels or at House-approved levels, whichever are lower, although defense is virtually assured some increase as soon as a bill providing new funding for the Pentagon is reported out of the Appropriations Committee.

This drew protests from some Democrats who complained that social programs were being shortchanged. Republicans also say the White House is concerned that it won't get as much as it wants for defense, although some GOP members said they believe Reagan's advisers don't want a veto confrontation over the interim spending bill. The OMB said no decisions have been made on the measure.

Meanwhile, Congressional Budget Office Director Alice M. Rivlin called on Congress to consider moving to a two-year budget, along with other steps to streamline its budget and appropriating processes, including automatic stopgap spending authority to eliminate "end-of-year brinksmanship" over funding the government.

Appearing before the Senate Budget Committee, Rivlin, who plans to retire in January, said the budget control process needs "further strengthening but not basic change." Much of this, she said, could be accomplished without total overhaul of the Budget Act.

Possibilities include adopting binding budget ceilings in the spring instead of fall and using an omnibus appropriations bill to "help reduce the current overload of the budget process on the legislative calendar."