We make explicit the intimate relationship between quasiexact solvability, as expounded, for example, by Ushveridze [Quasi-exactly Solvable Models in Quantum Mechanics (IOP, Bristol, 1993)], and the technique of separation of variables as it applies to specific superintegrable quantum Hamiltonians. It is the multiseparability of superintegrable systems that forces the existence of interesting families of polynomial solutions characteristic of quasiexact solvability that enables us to solve these systems in distinct ways and that gives us the basis of a classification theory. This connection is generalized in terms of the understanding of the role of finite solutions of quantum Hamiltonians