Just got back from the oriana, it dose not matter which dinning room you are in the menu will be the same, we were in the oriental, but the penisular is the other one and they are both very nice. They both have first and second dinning. the second seating is around 8.30. they do two shows in the thearter so which ever one you are on you will see the show.
It will be in either the Peninsular or the Oriental restaurant on E deck as both main restaurants are used. There will be a card in your cabin giving you the table number and which restaurant. The menus are identical.
It's a few years since I was last on Oriana but, in those pre Carnival days and when they had fewer ships, the brochure used to state which cabins were allocated to each restaurant. From what I recall the basic rule was that if your cabin was forward then you were allocated the Peninsular while those whose cabins were aft went to the Oriental. Don't take this as a hard and fast rule and if you have a suite then possibly different arrangements may apply. As Ingle has already stated, the menus are identical.
Just come back from Med. on Oriana, I agree with Ingle. Both restaurants are the same menu, and you will be told which one when you get to your cabin. I'ts a great ship,plenty to do or not as you wish,staff are fantastic and it is one of the best if you hit any rough weather - we had force 10 coming back across Biscay. Have a great cruise!!