What are the tanks dimentions?filteration?
The problem you have with this is you will need to purchase larger fish,also allow for aggresstion which oscar might take towards tankmates,if he's always been alone he might find others as a threat, however this aside,
In my 566 litre i have
1 pair of oscars
4 bala sharks
1 ornate birchir
2 pink tailed chalues
1 spotted silver dollar<a rescue and cannot find more his size>hes a wopper>
1 channa pleurophthalma
All with now aggresstion problems at all,most peaceful my tank has been