Sen. Jesse Helms (R-N.C.) may be the chairman, but they aren't playing follow-the-leader on his Senate Agriculture Committee debate.

The committee is expected to finish work today on a food-stamp bill that, at least so far, contains none of the major changes the chairman wants.

In a word, Chairman Helms has been rolled by a coalition of Democrats and Republicans who find themnselves in the curious position of defending President Reagan's plan for reducing food-stamp costs by about $1.4 billion next year.

Through yesterday, the committee had:

Rejected the Helms proposal to cut stamps benefits for families whose children receive free school lunches.

Turned down his proposal to require recipients to pay for part of their stamps, a feature that was removed from the program in 1979.

Defeated his effort to have low-income energy assistance counted as income in calculating stamp eligibility, a change that would have ended benefits for thousands.

Refused to go along with his idea for mandatory "workfare" -- that is, a requirement that recipients pay off stamp benefits by working for local governments without salary.

Defeated his scheme for tightening eligibility requirements, which he calculated might save at least $738 million and remove several million beneficiaries from the rules.

What was happening instead was that the committee was going along with Reagan administration proposals or, in several key instances, rejecting those for more moderate approaches offered in a package by Sens. Bob Dole (R-Kan.) and Patrick J. LEAHY (D-Vt.).

Dole-Leahy alternatives allowing free school lunches with no discounting of stamps (opposed by Reagan), optional "workfare" (supported by Reagan) and eligibility guidelines similar to Reagan's were adopted by the committee.

As the Senate worked yesterday, its counterpart committee on the House side also was putting final touches on its version of a food-stamp bill, with provisions closely paralleling Reagan proposals.

The man behind the Senate mini-revolt was Dole, who had worked for days to line up committee votes and, as a result, didn't lose a major roll call in the food-stamp battle.

At one point yesterday, after Dole voted a proxy left with him by conservative Roger Jepsen (R-Iowa), Helms was muttering. "He's a consponsor of my bill and he has been voting against me all day in absentia. I dont understand it."

Dole's big selling point was that his package would save about $200 million more than Reagan's would, but the savings would be achieved in less drastic ways while protecting children and the elderly.

Not that Helems did not win a few. The committee members went along with his ban on food stamps for strikers. They gave him their votes to stop stamps for drug- and alcohol-abuse centers, but wouldn't buy the same idea for centers for battered women and the handicapped.

A modified Dole-Leahy approach also prevailed on Puerto Rico, which gets $1 billion, about one-tenth of the annual food-stamp budget. Reagan wanted to cut nutrition aid by 24 percent and roll the remainder into a block grant for the commonwealth. As ameneded by David Pryor (D-Ark.), the cuts would begin Oct. 1, then increase April 1, when the block grant would take effect.

But it wasn't all that serious all the time. For a while they toyed with the idea of banning pretzel and potatochips purchases with food stamps.

And when Paula Hawkins (R-Fla.) called for quiet so she could talk about mandatory imprisonment for food-stamp cheaters (she backed away from that), she had a collegial exchange with Helems.

"Atta boy . . . uh, girl, lady, person," said Helms.

"I'm not a person," said the senator. "I'm a lady."

Chairman Helms was foiled again.