House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) said yesterday his committee will look carefully at the "generous modifications" made in President Reagan's tax plan before it was sent to Capitol Hill.

Rostenkowski said the committee will look with "a critical eye" at tax advantages for the oil and gas industry that the Treasury Department's original proposal would have tightened. In addition, he said, the committee probably will provide more tax relief for middle-income earners and that proposed changes affecting heavy industry in the Rust Belt will be reexamined.

Rostenkowski, appearing on ABC-TV's "This Week With David Brinkley," also said his committee probably will change the transition schedules in the president's tax revision, which would eliminate several large deductions on Jan. 1 but would not cut tax rates until July 1.

Rostenwkoski said one provision he would like to retain is the $1 checkoff for presidential campaign financing, something the administration proposed eliminating.

He expressed no opinion about eliminating the deduction for state and local taxes. But he agreed with New York Gov. Mario M. Cuomo (D), who appeared on the same program, that the administration had managed to compromise with almost everyone except state and local officials.

Treasury Secretary James A. Baker III, also appearing on the program, said the deduction amounts to a transfer of wealth from low-tax states, where the deduction means little, to high-tax states, where the deduction softens the impact of state and local levies.

"With respect to state and local deductions, if you should eliminate that from this proposal, I don't think you'll have tax reform," Baker said. "From a simple revenue standpoint, you're talking about $40 billion in 1990 . . . . You're just not going to find the revenue elsewhere. There's just too much money involved."

The Ways and Means Committee will hear from a group of corporate executives Tuesday, and other hearings during the week will focus on the economic effects of the plan and taxation of the poor. The Senate Finance Committee is to start holding hearings on June 11.

Rep. Richard A. Gephardt (D-Mo.), cosponsor of an alternative Democratic tax-revision plan, said yesterday that the Reagan proposal does not help the middle class as much as it aids the very rich and the very poor. Gephardt said on NBC-TV's "Meet The Press" that his bill is more favorable to those earning $30,000 to $40,000 per year.

Gephardt expressed doubt that Congress can resist the special-interest lobbies that will seek continuation of their tax preferences.

"This is going to be the biggest political brawl that Washington and the country have ever seen," Gephardt predicted. "When you change the tax code to this degree, you really affect everybody and every interest in the country. Every lobbyist in Washington will be hired to be inside the Ways and Means room. I still question whether or not we can produce a bill. It's going to be something nobody has ever witnessed before."