CBS announced yesterday that Phyllis George, who in January joined "The CBS Morning News" to great fanfare, but whose seven months there were marred by on-air gaffes and poor ratings, has left the program for good.

The network released a statement from George, in which she said she needed to "rearrange my priorities."

CBS announced that "effective immediately," life style and entertainment reporter Maria Shriver and network newcomer Forrest Sawyer, who have been cohosting the show this week while George has been on vacation, will become the new "permanent" coanchors of the troubled program, which has been perennially dead last against NBC's "Today" show and ABC's top-rated "Good Morning America."

Sources at CBS said that during the last three months, George had grown despondent about the show's problems and management had become anxious to replace her. Both parties realized the combination was not working, the sources said.

The separation "was obviously mutual," CBS Director of Communications Ann Morfogen said yesterday.

A former Miss America and former first lady of Kentucky, George, 35, is departing with more than two years left on a contract reportedly worth $1 million a year. The terms of her departure were not disclosed, and George's agent says she has asked to be reassigned outside the network's news division. "There is no assignment for her at CBS News," Morfogen said. "She'll be back at some point to tidy up her business and loose ends and whatever. Her office has not been cleaned out."

Forrest Sawyer will replace George's erstwhile coanchor, Bill Kurtis, who left the show in June to return to his old job as news anchor at WBBM-TV, the CBS-owned station in Chicago, while also doing programs for "CBS Reports."

"I certainly wish her well," Kurtis said yesterday. "She's a very nice lady and was a pleasure to work with." That was a marked change from what he was saying in interviews when he was working with her -- interviews over which George said she "confronted him." "There was no confrontation," Kurtis said yesterday.

George's husband, former Kentucky governor John Y. Brown, is reportedly considering a return race for governor in 1987. Sources said that George wants to be free to aid him in the race, and to spend more time with their two young children.

"The job has obviously been a strain on her, with great demands on her life and the governor's life," said Morfogen. "I know Phyllis has been, over the past several months, wondering about things like, 'I don't ever see my children.' "

George's agent, Ed Hookstratten, said "I was really surprised" when his client phoned him with the news yesterday morning from her family's vacation home in Lexington, Ky. "Her family comes first," he added. "But I knew how tough it was for her. She was sensitive to the press criticism that she didn't deserve."

The criticism was there from the rocky start, as George committed such flubs as asking comedian Billy Crystal if Fernando Lamas had ever called him about his famed impersonation (Lamas had been dead for years), and referring to Andrew Lloyd Webber as the composer of "Jesus Christ Superstore."

"I'm comfortable with who I am and what I'm doing and I've got to learn, and I'm the first to admit it, but when they start getting nit-picky, it hurts," George said after the first wave of criticism.

The bad notices reached their peak when George, during an interview last May of Gary Dotson, freed after six years in prison on a rape charge, and Cathleen Webb, the victim who changed her story to say Dotson was innocent, invited the two to hug each other on the air.

They declined the invitation, while people at competing networks branded it "incredibly poor taste," and "another entry to add to the laundry list of Phyllis George gaffes."

Late yesterday, after industry rumors of George's imminent departure surfaced, CBS released statements from George and CBS News President Edward M. Joyce.

"After two weeks' vacation with my family in Kentucky," George's statement went, "I have come to the conclusion to rearrange my priorities and thus informed Ed Joyce that I desire not to continue with my present CBS assignment. This is a personal as well as a professional decision."

Joyce's statement said in part: "All of us are grateful for the hard work Phyllis did for CBS News and we wish her and her family the best. I can understand how difficult this year has been for her and for her family, and we will miss her. We're delighted to have two extremely talented correspondents in Forrest Sawyer and Maria Shriver."

Sawyer, 35, a veteran of WAGA-TV, the CBS affiliate in Atlanta, began at the network in early July as a cohost of "The CBS Early Morning News." He popped up one night last week as a replacement for Dan Rather on the "CBS Evening News."

Shriver, 29, daughter of R. Sargent and Eunice Kennedy Shriver of Washington, joined CBS News' Los Angeles bureau two years ago after working as a West Coast reporter for the syndicated "PM Magazine."