It will be a little easier to learn the names of the major stockholders of publicly owned companies, thanks to new rules adopted yesterday by the Securities and Exchange Commission.

But the SEC, in its rulings, stopped short of calling for total disclosure of the owners of America's corporations.

In effect, the SEC formalized a reporting process that, at best, has been casually enforced. The new rules, which become effective on Aug. 31, broaden the definition of beneficial ownership of stock. As a result, more individuals will be forced to report their holdings.

A beneficial owner of a security, under the rules, is an individual or institution with the power to vote or direct the voting of a share of stock and the power the sell the share. In line with the recently popular trading in options, beneficial owners also include persons who have the right to acquire securities within 60 days.

By statute, when an investor acquires 5 per cent or more of a company's stock, he must tell the SEC within 10 days.

Under the new rules, the names of stockholders with more than 5 per cent of a company's shares will appear in such widely circulated publications as registration statements and proxy material.

The new rules say that a "group formed by two or more persons who agree to act together" to buy securities in a company must report to the SEC if their collective holdings exceed 5 per cent.

This rule is to block individuals from each buying less than 5 per cent, than banding together to gain effective control of a corporation.

The secret ownership of corporate stock by institutions, such as trust departments of banks and pension funds, has long troubled some legislators. A particularly outspoken critic of federal regulatory agencies for not demanding more disclosure of corporate ownership is Sen. Lee Metcalf (D-Wyo.)

Three years ago, Metcalf's subcommittee on reports, accounting and management probed the issue of how corporate stock ownership was often untraceable because the shares were listed under so-called nominee or street name accounts.

For example, a New York firm called Cede & Co. is a nominee for certain banks and for the Depository Trust Co., a subsidiary of the New York Stock Exchange. Its vaults hold an estimated 4 billion shares of stock in some 3,000 companies. Cede's name, not that of the bank, pension fund or individual investor, appears on the stock.

Now, however, if the real owner falls under the new beneficial ownership definition, and if he owns more than 5 per cent of the corporation's stock, his name - not Cede's - must be listed.

A steering committee, which grew out of the 1974 Metcalif subcommittee hearings on corporate ownership, recommended that the SEC and other regulators demand that corporations reveal the holdings of their 30 largest shareholders of record - not juse those with more than 5 per cent.

The SEC in its ruling yesterday, specifically declined to require that publicly held companies report the 30 largest stockholders.

The SEC said it dropped this 2-year-old proposal because it would not provide material information to investors, would be unnecessarily burden some to corporations and, in some instances, might involve an unwarranted invasion of privacy.

Vic Reinemer, who is a staff director of the Metcalf subcommittee, was critical of the SEC for this decision.