In this article, we study and settle several structural questions concerning
the exact solvability of the Olshanetsky-Perelomov quantum Hamiltonians
corresponding to an arbitrary root system. We show that these operators can be
written as linear combinations of certain basic operators admitting infinite
flags of invariant subspaces, namely the Laplacian and the logarithmic gradient
of invariant factors of the Weyl denominator. The coefficients of the
constituent linear combination become the coupling constants of the final
model. We also demonstr ate the $L^2$ completeness of the eigenfunctions
obtained by this procedure, and describe a straight-forward recursive procedure
based on the Freudenthal multiplicity formula for constructing the
eigenfunctions explicitly.