Greece's presidency said the ceremony would take place after Samaras meets President Karolos Papoulias and receives the formal mandate to govern.
Earlier Wednesday, New Democracy agreed with Socialist PASOK and the smaller Democratic Left party to form a coalition government after protracted negotiations. Despite receiving nearly 30 percent of the vote Sunday, the conservatives lacked enough seats to govern alone and had to seek partners that would also broadly back Greece's pledges to bailout creditors for further austerity and reforms.
The deal ended nearly seven weeks of political uncertainty in debt-crippled Greece that threatened to plunge Europe deeper into a financial crisis with global repercussions.
"Greece has a government," PASOK leader Evangelos Venizelos, a former finance minister, said after talks with Samaras Wednesday.
He added that the country will be represented at the upcoming meeting of Eurozone finance ministers by outgoing Finance Minister Giorgos Zanias.
The meeting "will be the first big battle on the revision of the bailout agreement, the creation of a framework that will allow us to move to positive growth and to combat unemployment which is the big problem of Greek society," Venizelos said.
Greek stocks rose in response to the news, with Athens shares up 0.6 percent in the afternoon, limiting earlier gains.
Both Venizelos and Samaras have pledged to try renegotiating some of the harsh austerity measures Greece had to take to secure its bailout loans - which would be stopped if Athens reneged on its commitments. The two parties are also looking for an extension of at least two years in the deadlines for implementing fresh cutbacks worth a total ?14.5 billion ($18.42 billion).
Democratic Left leader Fotis Kouvelis went a bit further Wednesday, saying that Greece should eventually "disengage" from the austerity commitments and "lift those measures that have literally bled society."
Over the past two and a half years, Greeks have suffered repeated income cuts, tax hikes and deteriorating public services amid a deep recession and galloping unemployment. In Sunday's vote - and the previous, inconclusive May 6 election - angry voters strongly favored parties promising to end the hardship by tearing up Greece's pledges for continued austerity and reforms.
However, the anti-austerity standard bearer - the radical left Syriza party - finished a narrow second in Sunday's election that gave New Democracy 129 of Parliament's 300 seats.
Earlier Wednesday, hundreds of poverty-stricken Greeks queued in a central Athens park for free vegetables. Cretan farmers handed out some 2,700 10-kilo packages of produce, in cooperation with the capital's municipal authorities.
Among the people lining up was Panayiota Sidera, 31, from Athens. She said she has been unemployed for two-and-a-half years and her husband is also out of a job. The couple is living on a ?250 monthly disability pension and rent from an apartment they own, and has a ?540-a-month loan installment to pay.
"That's my predicament," she said, adding that the food handout "is helping people, and I'm grateful."
"The government should have been doing this years ago," she said.