Jim Margolis, who held several key positions in the 1984 Democratic presidential campaign, has joined Greer & Associates, a Washington public relations, advertising and political consulting firm, as a senior associate.

Burson-Marsteller has named John Lengel, formerly with the public relations firms of Gray & Co. and Hill & Knowlton, vice president in its Washington office.

In a recent organizational restructuring, AT&T Communications announced two appointments in the company's eastern region, which includes Maryland, Virginia and the District: Kenneth L. Garrett, formerly vice president for marketing, has been named vice president for network organization. And Michael A. Brunner, recently vice president for government communications, has been appointed vice president for both marketing and government communications.

C & P Telephone Co. has announced three new assignments in its Washington headquarters: Clyde A. Heintzelman, formerly president of Bell Atlanticom Systems Inc., to vice president for sales; Ethan A. Stenger, previously programming manager, to assistant vice president for cost and economics, and Walter J. Burmeister, formerly a manager with Bell Communications Research, to assistant vice president for operations support. In addition, C & P's Virginia division has appointed Ernest J. Berger, formerly with Bell Atlantic Management Services Inc., as its Northern Virginia area manager. He replaces L. Robert Hardiman, who will become the company's regulation manager.