The Kingdom of Serbs, Croats and Slovenes was formed in 1918 and was initially divided into counties and districts (this division was inherited from previous state administrations).

Before 1922, the territory of the Belgrade Oblast was part of the Belgrade, Novi Sad, and Veliki Bečkerek districts.

In 1924, as a result of an adjustment of the border between the Kingdom of Serbs, Croats and Slovenes and Romania, the town of Žombolj (Jimbolia) was transferred to Romania.

According to the 1921 census, the oblast had a linguistically heterogeneous population: speakers of Serbo-Croatian were dominant in the cities of Belgrade, Pančevo, Veliki Bečkerek and Velika Kikinda, as well as in the districts of Belgrade, Umka, Kovačica, Veliki Bečkerek, Turski Bečej, Velika Kikinda, Titel and Žabalj; speakers of German were dominant in the district of Pančevo; speakers of Romanian were dominant in the district of Žombolj; while speakers of Hungarian were dominant in the city of Senta and in the districts of Senta, Stari Bečej and Turska Kanjiža.

[1] The oblast included the following districts: Besides these districts, several cities in the oblast had a separate status: The main cities and towns in the oblast were: All the mentioned cities and towns are nowadays in Serbia.