Which species of bichir are you looking for? I presume the senegal, correct? Bichirs stand a better chance handling your other fish than a ropefish can.
depends on the temperment of your oscar. if he's fairly laid back, and not aggressive at all, you could try a "dinosaur bichir" which would be a senegal most likely as Lupin said.
just be warned, a bichir can look like a worm to an oscar, and you very well could wake up to your oscar fatter then when you went to bed, and your tank minus 1 fish
large oscar, bichir will = dinner unless the poly is fairly large, or the oscar very tame IMO
not saying it cant be done, as i kept 3 small polys under 5" with a 12" oscar for several months. my oscar is also as mellow as can be, and bites my hand, not other fish
I had experience with dino bichirs and needlefish as they use to be present in my aquarium. The bichir chased the needlefish around until the needlefish bit it. It learned it's lesson =)
I would be afraid of the oscar. It would be like a dog in a tank vs a small dog. If however, the bichir is bigger than the oscar, the oscar would = dead meat. Also if the oscar was larger than the bichir then the situation is vice versa.
To me, ropefish = more rare, but senegals are a heck of a lot of fun. Never kept them with oscars, but maybe you could get away with it if the bichir was large.