Brandon Stoddard, who brought such mini-series classics as "Roots," "Winds of War" and "The Thorn Birds" to television, has been named president of ABC Entertainment and will immediately take charge of programming the struggling third-place network.

Frederick S. Pierce, president and chief operating officer of ABC Inc., announced Stoddard's promotion yesterday and also announced that Lewis H. Erlicht, president of ABC Entertainment since 1983, would become president of ABC Circle Films, the network's in-house production unit, which produces the series "Moonlighting," one of ABC's few current hits.

Stoddard will be, among other things, Erlicht's boss.

Immediate reaction in Hollywood, where Stoddard is widely admired, was "ecstatic," according to a spokesman for one of the major production houses. One reason ABC has slid to third place in prime time, industry sources have said, is that the network had poor relations with the producers who make its shows. ABC executives had earned a reputation for meddling and interference.

"Brandon Stoddard has a lot of class, and he has great relationships with the creative community," said producer David L. Wolper, whose mini-series "North and South" just earned huge ratings for the network. "I believe very strongly he's the right man at the right time for ABC," Wolper said from his Los Angeles office. "It will be very hard to find anyone to say anything bad about Brandon."

Wolper, who was also executive producer of "Roots" and produced the much acclaimed pageantry of the 1984 Los Angeles Olympics, compared the promotion of Stoddard at ABC to the arrival at NBC of Grant A. Tinker as chairman and chief executive officer in 1981. "I think he'll bring the same kind of tone and talent to ABC that Grant brought to NBC," Wolper said.

One studio executive said a chief difference between Erlicht's and Stoddard's approaches to programming is that "Erlicht was always most concerned with the commerciality of a project, while Brandon thinks first about quality -- although his projects always end up being commercial anyway." Viewers will probably notice an upgrading in the quality of ABC programs once Stoddard takes over, the source speculated.

The announcement yesterday followed Monday's news that Anthony D. Thomopoulos had resigned as president of the ABC Broadcast Group. The changes are part of a realignment of the company as it awaits the arrival of a new owner, Capital Cities Communications. Cap Cities will take over in January once its acquisition of ABC is approved by the FCC, which is expected to rule favorably tomorrow. An ABC spokeswoman said Cap Cities did not play a role in the newly announced executive shifts.

Stoddard had been offered the job of ABC Entertainment president several times before and turned it down, the spokeswoman confirmed. He accepted it this time, it was said, partly because ABC recently announced it was getting out of theatrical motion picture production, thereby narrowing the purview of his old job. One industry source said a highly decisive factor this time was that retiring ABC Chairman Leonard H. Goldenson took Stoddard aside and personally talked him into taking the job.

An ABC Entertainment spokesman said Stoddard was unavailable for comment.

Stoddard joined ABC in 1970 as director of daytime programming. Later, as a senior vice president, he helped develop such series as "The Love Boat," "Hart to Hart" and "Eight Is Enough." In a statement, Pierce hailed Stoddard as "one of the most experienced and talented executives in the entertainment business" and said he had made "enormous contributions to the quality of programming in our medium."

In various executive positions at ABC Entertainment over the past decade, Stoddard shepherded to the air not only high-rated mini-series like the record-breaking "Roots," but also such TV movies as "The Day After" and "Something About Amelia," which ABC says are the highest-rated TV movies ever aired. Stoddard, 48, is married to Mary Ann Dolan, a Los Angeles-based journalist who is an occasional panelist on the ABC News program "This Week With David Brinkley."

Stoddard's mini-series and prestigious, if sometimes controversial, movies were often said to be oases of taste and showmanship in an ABC prime-time schedule generally of less luster and quality than its competitors, even before the network's ratings slumped.

Although "North and South" pushed ABC to a rare win in last week's prime-time Nielsens, the network also dominated the bottom of the ratings, with five of the week's 10 lowest-rated shows, including "Diff'rent Strokes," "Benson," "Hollywood Beat," and "Our Family Honor."

For the record, the promotion of Stoddard increases to two the number of men named Brandon who head network programming divisions. The president of NBC Entertainment is Brandon Tartikoff.