Oliver supported Dušan in the succession war against his father, and was one of the supreme generals in the southern military expeditions (Macedonia, Thessaly).

[2] He ruled his domain, in modern-day North Macedonia, as a semi-independent prince, acknowledging Dušan's suzerainty but not subordinate to him.

[6] He was also active in the 1334 war with the Byzantine Empire, and was present during the subsequent peace negotiations together with Vratko Nemanjić, when Jovan was probably named despotes by Andronikos III Palaiologos.

[3] With the death of Hrelja in late 1342, when the latter's domain was split between Jovan Oliver and Dušan, he was able to further expand his lands, including the important towns of Štip and Strumica.

[7] Jovan Oliver outlived Dušan, but after his death, his sons were unable to assert themselves: possibly opposed by a coalition of other nobles, they failed to acquire any positions of importance, and most of their father's lands were taken over by Constantine and John, the sons of sebastokrator Dejan Dragaš of Kumanovo.