Now the giant lock links up with the Lions on Monday ahead of their May 24 departure date to South Africa.
Lions flanker David Wallace touched down twice - in either half - along with Denis Leamy and Paul Warwick, before replacement Anthony Horgan sealed maximum points on his final appearance for the Red Army.
James Hook scored all the visitors' points as the Ospreys lost for the second time in Limerick in as many months following their embarrassing 43-9 Heineken Cup defeat last month.
O'Connell was one of five Munster Lions on show with Wallace, Ronan O'Gara, Keith Earls and Donncha O'Callaghan also playing their final game before the tour of the Republic.
Munster: Tries - Warwick, Wallace (2), Leamy, Horgan; Cons: O'Gara (4); Pen; O'Gara
Ospreys: Try - Hook; Con: Hook; Pen: Hook