Depends, Are you certain it's 72" x 12" x 21", If so. Then no I wouldn't house two grown Oscars in this tank. And I wouldn't even be able to justify having 1 Grown Oscar in this tank. My 1 year old Oscar is about 10" long. He's in a 55G moving into a 150G this weekend. The footprint for the tank you have can't support a Full Grown Oscar.
However, If your tank is actually, a 72" x 18" x 21" Which is what I suspect. Then Yes you could house your Oscars in this tank.
Mike
However, If your tank is actually, a 72" x 18" x 21" Which is what I suspect. Then Yes you could house your Oscars in this tank.
Mike