The appointment followed a review of its international equity portfolio.
"The board decided that it would adopt a core satellite approach to managing this portfolio. Vanguard would manage the passive component, which makes up around 40 per cent of our international equities portfolio," LGSS chief executive Peter Lambert said.
As a result of the review, AQR Capital Management and AllianceBernstein were terminated.
"We are now looking for two new managers who are consistent with the appropriate styles that are now required in the portfolio," Lambert said.
LGSS manages around $5.7 billion in funds under management.
