The service at St John the Baptist Church in Shedfield, Hampshire.
Ossie died at the age of 59 after suffering a heart attack on 1 March.
Among those who attended were Saints chairman Rupert Lowe and the club's former managers Sir Alan Ball and Lawrie McMenemy.
Other mourners joining Osgood's wife Lynette included former Southampton and England striker Mick Channon, former Chelsea player Dennis Wise and Matt Le Tissier, former Southampton and England star.
Bouquets of flowers - some in the shape of his Chelsea and Southampton shirts - lined the approach to the church.