No guarantee as far as temperament with oscars, or any other cichlids for that matter. I got mine as a 1" auction fish that nobody wanted, as he grew he took a dislike to one of the albino bristlenose he grew up with. This incident requires netting, a wet towel, and a pair of needlenose pliers to remove the now dead bristlenose who had successfully wedged himself inside the oscar's mouth before dying.
This is the same oscar that later took a dislike to a 13" common plec that I was "gifted" with, along with a 72 gallon tank. One day the oscar got the better of him, took out the plec.
I've also seen more mellow oscars kept with large angels, long term, with no problems. It's all individual temperament, anyone dealing with cichlids should at the very least keep a divider handy, and have a backup plan beyond that.