James T. Aubrey Jr., a hard-driving television and film executive who headed CBS and then Metro-Goldwyn-Mayer, died on Sept. 3 at U.C.L.A. Medical Center in Los Angeles. He was 75 and lived in Los Angeles.

The cause was a heart attack, the Associated Press reported. It said paramedics found him unconscious, at a location it did not identify, after he had summoned them by telephone.

Mr. Aubrey was the president of CBS from 1959 to 1965 and of MGM from 1969 to 1973. Afterward, he was an independent producer.

While he ran CBS, it bloomed with top daytime dramas and glittered with top nighttime series. Among the Aubrey-era successes were "Green Acres," "The Dick Van Dyke Show" and "The Beverly Hillbillies."

But in those years, Mr. Aubrey earned a reputation not only as a supersalesman, but also as a ruthless cost-cutter. He reaped harsh criticism as well as respect. At CBS, he was described by some as "the smiling cobra," a phrase said to have been coined by John Houseman.

In Mr. Aubrey's years at MGM, which had sunk into debt before he arrived there, he did much to cut costs, overseeing a wide range of retrenchment measures. After his death, his son, James W. Aubrey, said: "MGM was in the red when he was hired, and within a year it was back on its feet and in the black. He sold the back lots, the props and all that. It wasn't popular, but it had to be done."

In 1973, the elder Mr. Aubrey surprised the film world by resigning as MGM's president. By that time, he had undeniably turned the company around, slashing its debt and putting it in the black. But numerous observers shared the view of Max Palevsky, a former industrialist who was then involved in movie production. He contended that Mr. Aubrey had done it "by selling off any part of the company that was profitable so that he could cover up his mistakes."

And others contended that Mr. Aubrey's management took an artistic toll as well. The New York Times critic Vincent Canby wrote in late 1973: "Unfortunately, Mr. Aubrey insisted on showing Hollywood what it was doing wrong by example. He made inexpensive films, which was a good idea, but they were almost uniformly bad, which wasn't." And Mr. Canby suggested that "when there was any chance that a film might be good, he, or someone else, interfered in the production." From Magazines to Broadcasting

Mr. Aubrey was born in LaSalle, Ill. He graduated from Phillips Exeter Academy and from Princeton in 1941. Then he worked as an account executive for magazines before moving into radio and then television. He became program manager for the CBS television network in Hollywood in the mid-1950's.

He rose to be a CBS Television network executive vice president before becoming president. Between his sojourns at the top of CBS and MGM, he worked for a time as an executive of ABC's television network.

Mr. Aubrey's 1944 marriage to Phyllis Thaxter ended in divorce.

In addition to his son, his survivors include a daughter, Skye.

Photo: James T. Aubrey Jr. (The New York Times, 1969)