Consumers will find less marbling in the beef they buy--perhaps as early as next fall--under a new grading program proposed yesterday by the Agriculture Department.

The proposal would reduce the requirements for marbling, the flecks of fat that traditionally have denoted beef juiciness, flavor and tenderness in "prime," "choice" and "good" grades sold by grocery stores and restaurants.

"Some meat that will qualify for choice under the proposed change would not qualify for choice now," said Tom Porter, a USDA marketing service official.

Consumer leaders immediately criticized the proposed grading standard, saying that it could lead to consumers paying more for cuts of lower quality.

The USDA proposal "is great for cattlemen and bad for consumers," said Tom Smith, an agricultural economist with the Community Nutrition Institute.

But the cattlemen's organization, which had sought the new standards, arguing that lower marbling requirements would give consumers leaner beef and help reduce production costs, were careful not to claim victory.

W. T. Berry, executive vice president of the National Cattlemen's Association, said that it would be premature to comment on the proposal "until we see how they word it . . . and how it compares with our proposal."

Porter said that the government's proposed changes don't go as far as the cattlemen had requested. Their petition, for example, had asked that moderately marbled beef from animals between the age of 9 and 30 months be bumped up from the "choice" grade into the more expensive "prime" grade. But the USDA proposal calls for that beef to remain in the "choice" grade, Porter said.

The cattlemen did prevail on some other points, however. For example, the group had asked that beef with slight marbling be graded as "choice" rather than "good." That would be permitted in some cases, according to the USDA proposal.

The debate over the beef grading standards began a year ago when the cattlemen's group filed a petition asking USDA to reduce the beef marbling requirements. Nineteen groups, representing meat wholesalers, middlemen, restaurants, cattlemen and consumers, submitted their own proposals, counterproposals and comments.

After sifting through the file, the USDA came up with the proposal that is published in today's Federal Register.

The department will be accepting comments on the propsal through March 30. In addition, it will hold five public hearings, including one Feb. 16 in Washington.

Final beef grading rules could be issued as early as this spring, making it possible for consumers to find the changes in retail store meat departments as early as next fall, USDA officials said.

Since the beef grading standards were first developed in 1916, they have been amended eight times. The last major change was made five years ago when the agency, in a case similar to the current one, granted an industry request to lower marbling requirements.

Now, the cattlemen have asked that the 1976 requirements be lowered even more. Such a change would enable the industry to "respond to a growing consumer demand for more lean beef," according to their petition. The group says that current rules lead to "considerable overfattening of some cattle" by producers who feed animals longer to get them into the "choice" grade. Changing the grading rules would shorten the feeding time and reduce producer costs for animals to qualify for "prime" and "choice" grades, NCA said.

But the Community Nutrition Institute says there is a better way to provide consumers with leaner beef.

"What the cattlemen proposed is a system that would lower quality standards for all beef," said Smith. "What we feel should have been done is . . . change the nomenclature to give consumers a new lean grade of beef." The institute's proposed name for the new grade: "Choice Light." name for the new grade: "Choice Light."