RICHMOND, Va. (AP) _ J. Stewart Bryan III, publisher of Richmond Newpapers Inc., has been elected chief operating officer of Media General Inc.

Bryan, the 51-year-old son of Media General chairman D. Tennant Bryan, will continue as publisher of the Richmond Times-Dispatch and The Richmond News Leader, the communications company said Thursday.

Media General also has hired two new corporate officers and promoted a third to the position of senior vice president.

James S. Evans, Media General president, on Friday said the change ''will strengthen significantly the management structure of our organization.''

In addition to publishing the Richmond papers, Media General publishes the Tampa (Fla.) Tribune and the Winston-Salem (N.C.) Journal and operates TV stations WXFL in Tampa, WCBD in Charleston, S.C., and WJKS in Jacksonville, Fla.

Bryan began his newspaper career in the circulation department of The Richmond News Leader. He was named publisher of the Richmond papers in 1978.

The Bryans, through a trust, control the B class of stock that elects six of Media General's directors. Media General's A stock elects three directors.

His appointment is the first change in Media General management since the July 2 death of James A. Linen IV, executive vice president. Linen, 51, died from injuries sustained in an accident in London while on vacation.

Some of the business unit heads who had reported to Linen will report to Bryan, Media General spokesman Robert W. Pendergast said.

In other Media General appointments, Marshall N. Morton has joined the company as senior vice president and Basil Snider as vice president. David L. Jordan has been promoted from vice president to senior vice president.

Morton, 44, who had been corporate vice president and controller of West Point Pepperell since 1986, will be responsible for finance and data processing.

Snider, 62, former president of Media General's Garden State Paper Co. subsidiary, will be in charge of newsprint holdings in New Jersey, Mexico and Georgia.

Jordan's new responsibilities will include staff activities that affect acquisitions, planning and investor relations.