The delegation's visit comes two days after the Honduran supreme court said Zelaya would face charges of violating the constitution if he returned to the country.
But the OAS foreign ministers are poised to pressure the post-coup government in accepting the terms of the San Jose accord, a proposal suggest by Oscar Arias, the Costa Rican president.
Under the accord, Zelaya would be allowed to return with diminished powers, but Micheletti had said he could not agree to the pact until the supreme court ruled on the matter.
The San Jose accord also calls for early elections and grants amnesty both to Zelaya for any alleged crimes and to those involved in the coup.
The US strongly backed the seven-nation mission, saying it supplied an aircraft that took the delegation to the Central American nation.
Ian Kelly, a state department spokesman, said: "We continue to believe that the Honduran people deserve a peaceful negotiated agreement to which all parties can commit, and that this accord presents the best opportunity."