NEW YORK (AP) -- The audience boost that the London Olympics provided for NBC's "Today" show has been short-lived.

The Nielsen Co. says ABC's "Good Morning America" beat "Today" in the ratings last week by an average margin of 162,000 viewers. "GMA" lost on Monday to "Today" but then won the next four days.

During the Olympics, "Today" dominated. It won each week by more than a million and a half viewers. Last week's ratings indicated that much of the gain came from new viewers who didn't stick around.

Meanwhile, Robin Roberts returned to "Good Morning America" on Monday after being gone for two weeks. She still faces bone marrow transplant surgery in the coming weeks.