It should be possible, but not likely to be successful with any plant that needs to be planted in the substrate since an Oscar will pull it up. You'll want to go with tough plants that attach to wood or rocks: anubias, java fern, bolbitis fern, mosses.
It is possible to have tankmates with an Oscar. Oscars, IME, aren't nearly as aggressive as most cichlids. Avoid fin nippers. In college, I had an oscar with a pike cichlid and a beautiful synodontis angelicus catfish. I didn't have any problems.