In a study of Viking feasting in Iceland conducted by Davide Zori, Jesse Byock, Egill Erlendsson, Steve Martin, Thomas Wake and Kevin J. Edwards the authors found that beef and beer were the principal elements of the Icelandic feast - both for "entrepreneurial" and "patron role" feast gatherings.

Their findings led them to conclude that anthropogenic deforestation made the raising, feeding and housing of cattle much more difficult as time went on. Caprinae such as sheep and goats were much easier to provide for and therefore comparatively less special; a fact which relegated them to a secondary food status relative to cattle. Eventually it was only aristocratic families of considerable wealth who were capable of managing these assets in such harsh conditions, and helped to confirm beef as the principle food item of choice to impress one's guests and potential partners.

"The overall ratio of 1.92 cattle to 1 caprine bone identified in the Viking Age faunal assemblage from Hrisbru suggests a preference for cattle raising, consistent with livestock management choices directed at sustaining a chiefly political economy." (157)

As for alcohol, their study shows that beer of fermented barley was the only commonly available alcoholic beverage in Iceland and was the sought after choice for Viking chieftains. However barley cultivation was difficult (the growing season was short), and labour intensive in Iceland, requiring the expensive importation of supplementary supplies from elsewhere.

"Feasting in Viking age Iceland: sustaining a chiefly political economy in a marginal environment" Antiquity (03/2013) Volume 87, Issue 335, pp. 150-165.

I haven't posted here before but I've been reading up on the Viking age for a while now. Most of the books I've read have the same answers but the one I've read the most and use as my source is The Viking Age: the Early Histories, Manners, and Customs of the Ancestors of the English Speaking Nations Vol.1 by Paul Chaillu Du Ohaillu. You can find it on Amazon.

Some feasts you would have to bring your own food, some would have everything supplied by the Gođi, either way the food was mostly the same. Usually some form of oxen, horse, sheep or boar would be killed and hung by its feet to bleed out and then boiled. Mead was served obviously but also Skyr, a type of milk (usually goat) that was fermented (? Not quite clear on how it was made but people still eat it) to the point of being thicker than yogurt and sometimes including cottage cheese like clumps. Some sort of bread also and dried fish, although dried fish was more akin to a trail meal than something you'd eat at a celebration.

Hope this helps.