Winfrey, 53, who backs the 46-year-old Illinois senator in his campaign for the White House, will appear at his rallies in Iowa on Saturday, and in South Carolina and New Hampshire on Sunday, the Associated Press reports.
Demand for tickets in all three states has been brisk, and the event in South Carolina has been moved from an 18,000-seat venue to an 80,000-seat football stadium due to the level of interest.
Winfrey's involvement is unusual, as she typically does not make political endorsements, despite being a hugely influential public figure. However, she publicly threw her support behind Obama back in May.
'I Believe in This Person'"I think that what he stands for, what he has proven that he can stand for, what he has shown was worth me going out on a limb for," she told CNN's Larry King at the time. "And I haven't done it in the past because I haven't felt that anybody, I didn't know anybody well enough to be able to say, I believe in this person."
In September, she organized a gala fundraiser in California that raised $3 million for the Obama campaign.
Most polls currently show Obama and Hillary Clinton in a statistical dead heat in Iowa, with Clinton leading in New Hampshire.
Obama is set to receive more high-wattage support on Monday at a "Generation Obama" concert in L.A. Celebrities who will reportedly be on hand include Jessica Biel, Taye Diggs and Scarlett Johansson.