A series of quaternary lanthanide halide cluster compounds ALa(6)I(12)Z with transition metal interstitials (principally Os) and alkali or alkaline-earth metal cations (A = Na, Mg, Ca, Sr) have been synthesized by high temperature solid state techniques. The compounds were structurally characterized by single crystal and powder X-ray diffraction methods. The new compounds are isotypic (R3, Z = 3) with rhombohedral R(7)X(12)Z (R = Sc, Y, La-Lu; X = Cl, Br, I; Z = transition or main group element) and contain nominally octahedral R6X12 units centered by interstitial Z. Here, the cation (A) rather than the seventh R occupies the isolated position between clusters along c as A(x)R(1-x) with 0 < x less than or equal to 1. The balance of the structure remains essentially unchanged. The refined X-ray crystal structures of NaLa6I12Os, (Ca0.906La0.094)La6I12Os, (Ca0.621La0.379)La6I12Os, SrLa6I12Os, and (Sr0.526La0.474)La6I12Os are reported, along with results of electrical resistivity and magnetic susceptibility measurements on these and some analogous phases. The phases are generally semiconductors, but the complex paramagnetic properties are not those of simple spin-only systems.