  In this article we discuss the interaction between the geometry of a
quaternion-Kahler manifold M and that of the Grassmannian G(3,g) of oriented
3-dimensional subspaces of a compact Lie algebra g. This interplay is described
mainly through the moment mapping induced by the action of a group G of
quaternionic isometries on M. We give an alternative expression for the
endomorphisms I_{1},I_{2},I_{3}, both in terms of the holonomy representation
of M and the structure of the Grassmannian's tangent space. A correspondence
between the solutions of respective twistor-type equations on M and G(3,g) is
provided.
