If you're planning to keep both oscars, then that tank will barely fit the two of them and unfortunately not the parrot. And that's just if your oscars turn out to be two females or a pair. If they're two males, they probably won't tolerate each other and you'll end up with a lot of fighting.
I think you could possibly keep one oscar and one parrot in that tank, if you had an Oscar that isn't too aggressive. Mine is as mellow as can be, and he loves any tankmate that is too large to consider food. The main issue you'll run into with two oscars is a huge bioload for that size tank, or aggression if you have two males.