WASHINGTON — The House easily overrode President Bush’s veto of a $307 billion farm bill last night, handing him the most significant legislative rebuff of his presidency after Republicans broke with the White House en masse to side with farm groups, anti-hunger advocates, and the biofuels industry.

With a Senate override vote all but guaranteed Thursday morning, Congress prepared to deliver only the second veto override of Mr. Bush’s presidency and the first on a major piece of legislation.

Yesterday’s events left Republicans arguing publicly over another lapse in their commitment to fiscal discipline. As with the first veto override, which saved the Water Resources Development Act last year, lawmakers of both parties stepped in to save a law that promised to shower billions of dollars on key constituents and home-district programs.

“The vote on the farm bill has definitely been a challenge, if you look at it as regaining our fiscal brand,” a Republican of Virginia and member of the GOP leadership, Rep. Eric Cantor, said.

Mr. Bush vetoed the 673-page bill at midday, declaring that “Americans sent us to Washington to achieve results and be good stewards of their hard-earned taxpayer dollars. This bill violates that fundamental commitment.” He objected to subsidies for wealthy agribusinesses at a time of high food prices and farm income. Hours later, the House voted 316 to 108 to override the veto, with 100 Republicans siding with 216 Democrats. The Senate voted last week, 81–15, to approve the bill.

“The principle purpose of agriculture policy in the United States is to guarantee we’re not as dependent on other countries for our food as we are for our fuel,” declared the House Republican Conference Chairman, Rep. Adam Putnam of Florida.