After being lobbied by a campaign featuring television's J.R. Ewing and the Fonz, a House subcommittee appears to be on the verge of giving the Hollywood studios and production community a major victory in its fight to block repeal of rules governing television program ownership and syndication practices.

About 120 House members are sponsoring legislation that would bar the Federal Communications Commission from changing the financial interest and syndication rules until 1988. The House telecommunications subcommittee is expected to pass the measure on Wednesday, after hearing testimony on the proposal.

The expected endorsement of the highly unusual legislation would come just one day before the FCC is expected to consider changes in the rules, which the three major television networks have sought to repeal.

"We are in very, very good shape in the House," said Michael Gardner, a Washington lawyer representing a Hollywood coalition bitterly fighting the networks' effort. "I think there is basically a pervasive anti-network feeling within the Congress."

The Hollywood coalition, the Committee for Prudent Deregulation, has rolled out a number of television and film celebrities in recent weeks in an effort to gain support for the legislation. The bill's sponsors include Rep. Henry Waxman (D-Calif.), whose district covers much of the film community, and Rep. Timothy Wirth (D.-Colo.), the subcommittee's chairman.

All but one of the subcommittee's Democratic members support the Waxman proposal, making its endorsement by that panel all but certain. "The whole thing is a charade," charged one top network official who complained that network representatives were not informed of this week's upcoming hearing until they received a letter dated last Wednesday.

Larry Hagman, who plays the leader of the Ewing family on the CBS show "Dallas," recently hosted a reception for members of the House delegation from Texas and subsequently visited a number of other House members to make the Hollywood case. In addition, Henry Winkler, who plays the Fonz in "Happy Days"; actor Hal Linden, who plays Barney Miller in the show of the same name, and writers Norman Lear and Alex Haley have joined the lobbying campaign.

What makes the legislative effort so unusual is the flat prohibition against the FCC's taking any action, even before it votes on the matter. The FCC, which announced plans to take up the matter on Thursday, is searching for a compromise that might please the warring film and television network industries.

Although FCC Chairman Mark Fowler is widely considered to be firmly in the networks' corner, his staff is working up a compromise that would basically lift the restrictions on network program ownership while limiting their syndication role. Some network officials say privately they are willing to accept a Fowler-crafted compromise, but the studio representatives are expressing doubts. "I think it will be unacceptable and inefficient," Gardner said.

At present, the rules essentially bar American Broadcasting Cos. Inc., CBS Inc., and National Broadcasting Co. Inc., from program syndication and from acquiring interest in programs produced by others.

The networks argue that the rules are antiquated in light of competition from other media, while the production community says the rules prevent domination of the programming production business by its three most significant distributors.

Some network executives are particularly upset about what they view as a bypassing of the administrative process. "The commission has been trying to reach a judgment using its expertise and the agency ought to be able to do its job," said Cory Dunham, executive vice president and general counsel of NBC. "On the face of it, it's unfair."

Network representatives also say it is highly unlikely the full Congress will adopt the Waxman proposal. "We are confident that Congress will not reregulate the industry to protect special interests after the FCC's long, thoughtful analysis," said David Boies, an attorney representing CBS.

Sources close to the studio group say, however, they are close to lining up Senate sponsorship for the measure. But they were unsuccessful last week in an effort--reportedly endorsed by Sen. Ted Stevens (R-Alaska)--to attach a rider to a Senate appropriations bill that would have barred the FCC from using money in the current proceeding. Sources say, however, it could be revived before the congressional August recess.