President Reagan today chided Israel and the Arab nations for failing to grasp the "opportunities" offered by his year-old Mideast peace proposals.

In a speech to a GOP women's group here, Reagan made passing reference to the proposals nearly a year after he outlined them.

Last Sept. 1, Reagan had proposed a resolution of the Palestinian problem by taking the West Bank and the Gaza Strip and, with some territorial adjustments, allowing self-determination for the Palestinians "in association with Jordan."

The proposal was rejected out of hand by Israel. King Hussein of Jordan said he would need the approval of the Palestine Liberation Organization, which subsequently rejected the Reagan initiative.

"The Mideast peace initiative which we announced almost one year ago is definitely alive and available to those parties willing to sit down and talk," Reagan said today.

He added, "It's unfortunate that neither Israel nor its Arab neighbors have yet grasped the opportunities afforded. We remain committed to the positions we set forth, positions that remain sound, positions that thus far are the only realistic basis for a solution. We will continue the pursuit for peace in the Middle East."

Reagan also prefaced his comment on the Mideast by saying the Marines in Lebanon are "increasing the chances for a peaceful settlement there."

"No one should think that our current efforts there mean that we are any less concerned about solving the broader problems of the Arab-Israeli conflict, particularly the search to reach a fair and practical solution to the Palestinian problem."

Reagan is expected to discuss the Mideast again Saturday in his weekly radio address.