I know I used to think that it would be absurd to put an angel with an oscar... BUT, if you put a juvenille oscar of around 2'' with an adult angel of 5''+ then I do believe that you could get away with it. Even an adult oscar isn't going to try to eat a good sized angelfish, (not only are they not pintsized, but boy do those fins make them look bigger than they are).
That coupled with the fact that oscars are the gentle giants of the cichlid world...
Just to back this a little, I find the fish profiles on this website extremely reliable and he says that you can combine them. Some day, if I ever have the space, I would like to try and see if it really works out.
http://aquaworld.netfirms.com/Cichlidae/Astronotus_ocellatus.htm