Let me start off by saying that I'm tough to please when it comes to seafood, probably has something to do with growing up on an island...
I must say that Oscar's is very clean and the staff is extremely friendly and courteous, overall it was a nice experience. I had the broiled Cod; I would say it's mediocre. My husband had the Ahi sandwich, which was better than the Cod, but not the best I've had. In both cases you could clearly taste the 'frozen' fish. We got a side of clam chowder to share; it was full of flavor and the best item out of everything we ordered (still not the best I've had...I will say the best in AZ so far).
It seems that the thing to get at Oscar's is the fish and chips. Frying a fish can make any bad fish taste good so I'll take everyone's word for it.
Not sure what kind of expectations I had, perhaps I NEED to remind myself that we ARE in Arizona. For what it's worth, my husband seemed to really like it! My three stars are for 1) a clean restaurant and friendly staff, 2) my husband liked it and 3) the decent clam chowder