The magnetic ground state in geometrically frustrated lanthanide oxides is determined by the interplay between different magnetic interactions and crystal electric field (CEF) effects. We have recently the effect of chemical pressure on the magnetic properties of the frustrated lanthanide garnets, Ln3A2X3O12, by varying the non-magnetic cations A and X. Magnetic ordering features are observed for all garnets with Ln = Tb, Dy, Ho; however the nature of ordering varies for different Ln as well as for different combinations of A and X. The magnitude of exchange and dipolar interactions are found to be similar for all the garnets. Therefore it is postulated that the variations in magnetic ordering are caused by subtle differences in the CEF. We propose inelastic neutron scattering experiments on MERLIN to precisely determine the CEF levels for garnets with Ln = Tb, Dy, Ho.