I'm wondering how a pair of Red Oscars will do with a non-spiny, [classified] non-aggressive, herbivorous catfish. If I can find these, here are the species that I have in mind:
Suckermouth Catfish: Hypostomus multiradiatus 12in or Hypostomus plecostomus 18in

welcome to the forum

most people will tell you that oscras can be very teratorial and it is a trial and error thing.

how big is your tank?

125 gallons, as suggested on this site.

However, I'm beginning to reconsider the difficulties of an Oscar and would like to also get an opinion on a single oscar with a catfish in a 75 gallon tank.

depends on how big of a catfish you choose..if you choose a sensible sized one and not one like a red tail then i think you would be fine..

i now have 2 oscar and a 12 inch pleco in a 90g...

you should have no probs with any species of pleco you want in a 125 with only 2 oscars as long as your filtration is adequate.

I am thinking of one oscar and one pleco (not sure what size... What should I get?) in a 75 gallon tank... No longer considering an oscar pair, just a single. 90 gallons sounds a little small for that setup, but they're probably small now.

Anyone? 75 gallons with general pleco and one oscar?