If the smaller fish have some height. If they are like dojo loaches then they’ll get eaten. If not able to be eaten it may get picked on by the Oscar. Tank info and tankmates needed to help.
If they can fit it in their mouth they will eat it. Sometimes they will be ok for a while, but eventually anything that will fit in it's mouth will be a snack.
been there done that. I have had to net an Oscar and pull the fish out of its mouth that was no way in world was it going to be able to get it down but was not going to spit it out.
What size is your current tank?
And...what kind of fish are in it now?
This belongs in the South American section, oscar are not endemic to Central America
If the smaller fish have some height. If they are like dojo loaches then they’ll get eaten. If not able to be eaten it may get picked on by the Oscar. Tank info and tankmates needed to help.