The move temporarily sidelines Honduras from any participation in the OAS, but obliges it to continue observing the body's rules in areas such as human rights.
Following the OAS announcement, Zelaya said he would return to Honduras on Sunday.
He was removed him from power as he was about to press ahead with a non-binding referendum that his domestic critics said was aimed at changing the constitution to enable him to run again for office.
Vow to return
Speaking to Al Jazeera after he arrived in Washington DC on Saturday for the emergency session of the OAS, Zelaya called on his supporters to prepare for his arrival.
"We are going to show up at the Honduras International Airport in Tegucigalpa ... and on Sunday we will be in Tegucigalpa," he said.
Lucia Newman, Al Jazeera's Latin America editor, said Zelaya thanked the international community for taking a firm stance, saying it had given hope to the people of Latin America and in these times there could not be silence."
More than 10,000 supporters gathered near the heavily guarded presidential palace on Saturday and pledged they would be ready if Zelaya returned.
Colin Harding, a Latin America analyst in London, says Zelaya is "hoping to force a showdown" by returning to Honduras.
"I think he wants to provoke the interim regime in Honduras into trying to arrest him. I think there is a certain sort of martyrdom attitude in the air," he told Al Jazeera.
"It's possible that we've got brinkmanship here, which will lead to some sort of compromise, which may conceivably allow Zelaya to return at a later date, to bring forward to election date to save the face of both sides," he said.
In earlier comments to a local radio station, Zelaya said he would be accompanied on his return by Cristina Fernandez and Rafael Correa, respectively the presidents of Argentina and Ecuador, in addition to several foreign ministers and 300 journalists.
"I ask all farmers, residents, Indians, young people and all workers' groups, businessmen and friends ... to accompany me on my return to Honduras," Zelaya said.
"Do not bring weapons. Practise what I have always preached, which is non-violence. Let them be the ones who use violence, weapons and repression.
"I hold the coup plotters responsible for the lives of each and every person."
Oscar Andres Rodriguez, the highest ranking Catholic Church official in Honduras, urged Zelaya not to come back.
"We think that a return to the country at this time could unleash a bloodbath in the country," Rodgriguez said on national television.
"To this day, no Honduran has died. Please meditate because afterwards it would be too late."
Our Latin America editor said: "It is very difficult to imagine that when Zelaya returns, as he said he will, it will be a bloodless event."
Significantly, before the OAS announced the Saturday deadline, the interim government declared that it was pulling out of the body rather than meet the demand.
"It is better to pay this high price ... than live undignified and bow our heads to the demands of foreign governments," Roberto Micheletti, the interim president, said.
However, OAS officials said that they would not recognise the interim government's decision to withdraw.
Al Jazeera's Nick Spicer, reporting from Washington, said OAS leaders called the request to leave the OAS illegitimate, because the bloc does not regard the current Honduran government legitimate.