Endohedral fullerenes form a unique family of carbon nanostructures with high stability and interesting properties. The encapsulated molecule or cluster can determine the properties of the fullerenes. Often charge transfer occurs from the endohedral unit to the outer cage leading to high stability. In this work we have examined the electronic properties of several transition metal oxide clusters encapsulated within a carbon cage. The chosen transition metal clusters have cubane structures with high spin. The motivation is to examine whether the encapsulation can stabilize transition metal clusters with high magnetic anisotropy energy. We are calculating the electronic and magnetic properties of Co4O4@C80, Co4O4@C78, Co4O4@C76, Co4O4@C70, Co4O4@C68 using density functional theory. The magnetic anisotropy energy of these endohedral fullerenes is calculated using a perturbative approach. Such magnetic clusters can have potential application in magnetic storage devices.