The relaunch of a slimmed down four-section paper will also see the return of the seven-day TV listings, which were controversially dropped back in July.
The cost-cutting relaunch will see The Observer drop its separate Escape, Cash and Business sections along with three of its four monthly magazine supplements - Woman, Music and Sport. The only monthly magazine to survive the cull is the Food supplement.
The new four-section paper will comprise an expanded main newspaper; a 56-page Berliner-size New Review supplement including science and nature coverage alongside TV listings; Sport; and the Magazine, which has been redesigned and includes more coverage of food, travel, fashion, relationships and gardening.
The Observer is launching its new look with an exclusive serialisation of Andrew Rawnsley's book on Labour in Government called "The End of the Party".
In his first major interview since taking over as Observer editor two years ago, John Mulholland told Press Gazette that the Rawnsley excerpts will not appear in full online at midnight on Sunday morning with the rest of the paper.
He said: "It's an extremely revealing detailed history of the Labour party in Government from 2001 to the end of 2009, we'll print approximately 10,000 words in that issue of February 21. They won't be made available across the web from midnight, we will release that at a later stage."
Explaining the reasons behind the move, he said: "Because we've paid good money. This is a property which virtually every other newspaper in Britain wanted, it's been the result of an incredibly amount of work on Andrew's part, I think it's reasonable in this particular case to say you might need to actually leave the house and buy the paper to avail yourself instantly on Sunday morning of the kind of work and effort that Andrew's put into that book."
Currently the entire editorial content of The Observer, including its supplements, is made available for free at midnight the day the newspaper comes out. But Mulholland said that conversations are now underway about how that policy may be changed.
Guardian and Observer editor-in-chief Alan Rusbridger restated his strong belief in the free dissemination of news online in a lecture at the London College of Communications last month.
Mulholland said: "We're all as a company committed to the kind of philosophy of openness and engaged mutualisation that Alan outlined at the Cudlipp lecture. But there are parts of what we do on a Saturday and Sunday which are not core to that kind of philosophy."
He later emphasised that at present this "staged release" policy only applies to the Rawnsley interview, and also possibly to the Observer crossword.
The relaunch of a slimmed down Observer follows a review Guardian News and Media held last summer which looked at closing the 219-year-old title as part of a range of cost-cutting options aimed at curbing GNM's 2008/2009 losses of £36.8m
This prompted public outcry and a campaign to save the paper led by the National Union of Journalists and Press Gazette.
When GNM revealed in November that The Observer was to be saved, but in a slimmed down form, the NUJ said the move was "extremely worrying" and showed that GNM did not have a "genuine commitment to the long-term future of the title".
Responding to this suggestion that the relaunch was really about killing The Observer by stealth, Mulholland said: "If anybody concludes after reading the paper on February 21 that this is something that is being killed off then I would be interested to know what an Observer would look like that isn't being killed off.
"There's a lot of resource a lot of talent and a lot of effort that has gone into not killing The Observer, but into giving it a new lease of life."
John Mulholland's full interview with Press Gazette will appear in the March issue of the magazine, which is only available to subscribers.
Dominic Ponsford is the editor of Press Gazette