In general.

In general, the early medieval Scandinavians ate a bit more fish and meat and a little less cereal than other Europeans at this time. They also ate more peas and other plants rich in protein. The diet varied heavily with the region - in coastal places, salt (or in case of the Baltic Sea, brackish) water fish, shellfish, sea fowl and sea fowl eggs were common, while grain, peas, cabbages and fresh water fish was more common inland. For regular people, every day food was pretty bland and unvaried. Vikings according to the sagas seem to have eaten two meals per day, perhaps with lighter snacks in between. Meals were usually served warm or hot, as it was hard to keep even indoor temperature comfortable (10-13 degrees C seem to have been common in early medieveal longhouses during winter). Boiling was considered the finest way to prepare a meal, and a caultron would be a very prized possession. Many people without access to cauldrons seem to have used clay pots with cooking rocks (rocks heated in fire and then places in the pot) to boil food. Searing or frying was not unknown for fresh meat. Especially salted meat leeches out salt in a soup or stew if boiled, so it was probably a good idea to prepare salted fish or meat that way.

Early medieval Scandinavians usually ate with a knife and a spoon (which could be deep like a soup spoon or more flat like a shovel) out of a large wooden through from which all ate.

Meat and fish.

Pork was considered the best meat, and outside the rich and powerful, or rarely as a luxury, was the only meat rasied explictly for consumption. Sheep were kept for wool, goats and cows for milk, horses for transport, hens for eggs and while they may be slaughtered for meat once they were not performing their primary task as well anymore, pigs were slaughtered when relatively young. Wild game was also hunted or trapped and included hare, elk, wild boar, deer and moose. According to the medieval county laws, based on older oral tradition, hunting was free in early medieval Scandinavia.

Herring and cod were the most common fish eaten, but bass, pike, salmon, trout and whitefish were also common. Seal, whale (and blubber of both) and shellfish were also commonly eaten in coastal regions. With the introduction of christian lent, Norwegian dried cod became a major export product and was widely eaten in Scandinavia as well.

In general all parts of an animal was used - blood, intestines, bone marrow were all used in various dishes, including blood bread, saucades and lung mash.

Food was preserved by drying, smoking or salting.

Grain.

Cereal was common, but not as dominating as further south. Wheat was rare - barley, oats and rye were the most common ones, baked into bread (which could also contain flour from peas and in hungrier times, bark from trees), boiled into porridge or gruel. One of the more common ways to preserve cereal was to brew it into a weak (1-2%) and cloudy dark beer that was drunk by everyone, including children.

Bread was often baked into thin, hard unleavened cakes akin to modern Swedish cripsbread.

Vegetables.

Turnips and white and red cabbage were common staple food. Peas, beans, radishes, carrots, yellow onions, leek, celery, spinach and kale were also common.

Dairy and eggs.

Milk from goats were common, cow milk was rarer. Dairy was mostly used in cooking, or to make cheese, yoghurt-like sourmilk, cottage cheese or butter. Whey (often soured) was used both to consume on its own and to preserve meat and vegetables. Drinking milk was rarer, but not unheard of.

Eggs, both from domesticated geese and chicken and gathered wild sea fowl eggs were eaten.

Fruit, berries and nuts.

Fruits were eaten as available and in season - mostly apples, but also plums, sloes and prunes. Berries were also common - cherries, blackberries, raspberries, lingonberries, blueberries and elderberries. Nuts, such as hazelnut and walnut was not uncommon either.

Spices.

Locally grown spices, such as horseradish, mustard seeds, angelica, garlic, dill, thyme, cummin, fennel, lovage and sweet gale were used extensively.

Drink.

Weak cloudy dark beer (1-2% ABV) brewed on the farm or estate was very common, otherwise water or more rarely milk was drun.

Luxuries.

Luxuries, for feasts and celbrations (such as weddings, coming of age, funerals and so on) were rare and expensive and were often imports. Mead was made from honey and a distinct luxury. Honey was overall a luxury that recuired a lot of labour to produce, but pretty much the only sweetener. White salt was rare and spices, including pepper could be available at high cost. "Double beer" (at times refered to as rowing beer, dragging beer, feastive beer etc) was a stronger beer (4-6% ABV) made by specialised brewers and were imported for feasts, as was wine from the Rhine valley. Veal and poultry rasied with the intention to slaughter and eat them and white wheat bread were also rare luxuries. Linseed and hempseed oil could also be used, but were also luxuries.

Dishes.

Two dishes still eaten in Sweden that probably originated in viking times or even earlier are "dopp i grytan" (dipping bread in pork broth as christmas meat is being cooked) and pea soup (yellow pea soup with pork).

Sources:

Vikingen (The Viking) by Bertil Almgren.

Från krog till krog (From pub to pub) by Håkan Jönsson and Richard Tellström.

Smaka på historien (Taste history) by Katarina Schoerner Carr