The club from the south of France announced that Garcia and his assistant, the former goalkeeper Zubizarreta, would both extend their stays at the Stade Velodrome.
They are now under contract at last season's Europa League finalists until 2021, signing on for another two years.
"Champion of France with Lille, Garcia took over from Frank Passi. In his first complete season, he lead the club to the Europa League final against Atletico Madrid, as well as finishing 4th in the league," the club said in a statement.
"After gaining experience as sporting director of Athletic Bilbao (2001-2003) and FC Barcelona (2010-2015), Andoni Zubizarreta is also in the long run. The former Spanish goalkeeper (126 caps) will continue his substantive work to ensure the development of the club on all fronts. Assisted by Albert Valentin, the 57-year old Basque is at the origin of the restructuring of the OM academy. OM Campus, a state-of-the-art training tool, was inaugurated last October 14th."