A Bay Area foundation has pledged up to $50 million to help needy students at California community colleges in what is believed to be the largest gift ever donated to the nation's two-year institutions.

The San Francisco-based Bernard Osher Foundation today plans to announce the gift, which will create an endowment to be managed by the Foundation for California Community Colleges. Half the donation--$25 million--will be paid immediately, while the other half will be paid over the next three years--as long as the foundation is able to collect $50 million of its own during that time.

The foundation has given millions to universities over the past few years, but it just recently became clear that community colleges needed significantly more financial help, said Mary Bitterman, the foundation's president.

"The more we have focused on the needs of California, we have really begun to look at the critical role community colleges play," she said. "What you read about is David Rockefeller giving $100 million to Harvard. Our trustees decided that we would really like to help community-college students." Another donation to be announced today will provide $20 million to several California public universities to help community-college transfer students.