There is so much to love about Norway (and I can't wait to go back one day). As usual, I was excited for the food, and hoping to try some great fish dishes. While it's true that Oslo is not a particularly budget friendly city, I think you'll find that a meal here is well worth the money.
Amundsen Bryggeri og Spiseri: Don't screw up here and order a hamburger here like my husband did! (To be fair, the place initially seems like a good place to have bar food and not more upscale fish dishes.) Instead, try the Cured Halibut as a starter and then get the Arctic Char for your main (you can thank me later). This place far exceeded our expectations. And they make their own ice cream and sorbet - so don't skip dessert!
Elias Mat & Sånt: A small place with great food, this was probably my favorite meal in Oslo. We had pumpkin soup and baked chevre to start; oven baked salmon and trollkrem for dessert - a lingonberry mousse that was as light as air! (One of those dishes you eat up before you can even think about taking a picture!) I am also curious about the reindeer stew; I would love to try it.
Den Glade Gris: Literally means "The Happy Pig" and although I'm not sure how happy the pigs here actually are, they are pretty tasty. They're known for their pork knuckle, which is basically a giant pork shank with vegetables. It's a lot of food, so I would recommend splitting it. The appetizers were good, and I suspect some of their less popular dishes are as well. After you eat, you can go up to the Summit Bar in the Renaissance for a great view of Oslo.
Mathallen Oslo: Mathallen is a popular indoor food market with over 30 vendors to choose from, so you're sure to find something here that you like. And, if you're interested in saving some money, this could be a great place to check out while you buy some supplies to make yourself a meal one night or create a picnic lunch.
A note on bars and cafes: Norway has a growing brewery scene and I was lucky to try a few Norwegian beers while in Oslo. Make sure you try some if you can! There's also a great cafe culture in Norway, and Norwegians like their coffee (but, similar to the cafes in Iceland I mentioned in my Iceland post, they have some good tea selections, too!). I really enjoyed getting a cup of tea and a pastry or two and just watching people go about their day on the street. There are cafes everywhere, so stop into one when you have a chance! They're also great for a relatively inexpensive, quicker lunch as you're hopping between sites.