"I just want to thank the president for hosting us," the president-elect said, flanked by former President George H.W. Bush on one side and his son on the other.
Presidents Bill Clinton and Jimmy Carter, both smiling broadly, stood with them.
"All the gentlemen here understand both the pressures and possibilities of this office," Mr. Obama said. "For me to have the opportunity to get advice, good counsel and fellowship with these individuals is extraordinary."
In a swift photo opportunity, the current president wished Mr. Obama well before all five men headed to a private lunch.
"I want to thank the president-elect for joining the ex-presidents for lunch," Mr. Bush said, even though he's not quite a member of that club yet.
"One message that I have and I think we all share is that we want you to succeed. Whether we're Democrat or Republican we care deeply about this country," Mr. Bush said. "All of us who have served in this office understand that the office itself transcends the individual."
He added: "We wish you all the very best, and so does the country."
The lunch was Mr. Obama's idea and President Bush thought it was a "fantastic idea," according to his press secretary.
And it represented an unprecedented gathering of America's past, present and future presidents, reports CBS News senior White House correspondent Bill Plante.
Ex-presidents are usually seen all together only at funerals or presidential library openings. President Ronald Reagan asked former presidents Ford, Carter and Nixon to attend the funeral of slain Egyptian President Anwar Sadat - the last time all the living ex-presidents were at the White House. President Clinton and the elder President Bush teamed up for good will missions such as hurricane or tsunami relief.
"What we've seen in American history is sometimes ex-presidents rallying together to do things," presidential historian Douglas Brinkley told CBS News. "But what's unique about this is Obama is making a real statement that I'm going to be seeking counsel and advice from all the ex-presidents."
It is the ultimate power lunch, writes CBS Radio News correspondent Peter Maer. The current and former presidents can brief Mr. Obama on their own experiences.
Above all, they can convey a sense of what has been described as "the loneliest job in the world," writes Maer. Andrew Jackson described the presidency as "dignified slavery." James Buchanan was reported to have told his successor Abraham Lincoln, "If you are as happy entering this house as I am leaving, you are the happiest man in the world."
Sitting presidents have often talked to their predecessors in the past. John F. Kennedy sought advice from former presidents Dwight Eisenhower and Harry Truman.
"It's not as though these men didn't make mistakes," political analyst Stuart Rothenberg told CBS News. "But maybe the fact they have made mistakes make them the kinds of people who an incoming president would want to listen to."
Mr. Bush and Mr. Obama also met privately for roughly 30 minutes. That one-on-one meeting, coming just 13 days before Mr. Obama's inauguration, likely focused on grim current events, with war in the Gaza Strip and the economy in a recession.
Mr. Obama has sought to strike a balance as the power curve bends his way. Before taking office, he is publicly rallying Congress behind a massive economic stimulus plan. But he remains deferential to Bush on foreign affairs and will not comment on Israel's deadly conflict with Hamas on grounds that doing so would be dangerous for the United States.
"You can't have two administrations running foreign policy at the same time," Mr. Obama said at a news conference earlier in the day.
Vice President-elect Joe Biden also held a private meeting with former President Bush at the White House on Wednesday.
Considering the bond they hold in history, U.S. presidents gets together infrequently, particularly at the White House. And when they are in the same room, it is usually for a milestone or somber moment - a funeral of a world leader, an opening of a presidential library, a commemoration of history.
Not this time.
"It's going to be an interesting lunch," Mr. Bush told an interviewer recently. When asked what the five men would talk about, Mr. Bush said: "I don't know. I'm sure (Obama's) going to ask us all questions, I would guess. If not, we'll just share war stories."
They have plenty of those, political and otherwise. Their paths to power have long been entwined.
Carter lost the presidency to Ronald Reagan, whose running mate was George H.W. Bush. Bush later won election but lost after one term to Clinton. Then Bush's son, the current president, defeated Clinton's vice president, Al Gore. And this year Obama won after long linking his opponent, John McCain, to Bush.
Those campaign rivalries tend to soften over time as presidents leave the White House and try to adopt the role of statesmen - although Carter, even as an ex-president, has had some critical public words for the current president's foreign policy.
All five men were to pose for a group photo in the Rose Garden, but a January rainstorm scrapped that plan. So the noontime photo opportunity - the media's only glimpse of them - was moved indoors to the Oval Office.
The presidents and Mr. Obama were having lunch in a private dining room off the Oval Office, where no one else was expected to join them.
"All of us would love to be flies on the wall and listening to that conversation," White House press secretary Dana Perino said.
The rare presidential joint appearance also offered Bush, who ends his two terms deeply unpopular, to again show he is rising above the fray.
And it represents one of the few times Vice President Dick Cheney has been left out of a big White House event. But in a radio interview with CBS News, Cheney said he doesn't feel left out.
"No, I'd love to be there, but the vice presidents weren't invited." He said today's lunch is "just for the big dogs."