Fast Days in the Middle Ages
Meat was forbidden by Church law on Wednesdays, Fridays and Saturdays and also during Lent, when the consumption of eggs was also forbidden. (Friday is commonly known to be a day on which fish was eaten, but Wednesday and Saturday are a bit more obscure. Find out a bit more about fast days here.)
These days were known as ‘fish days’. However, some communities would get round the prohibition of meat by eating barnacle geese, which was supposed to be more fish than fowl. According to Wikipedia, http://en.wikipedia.org/wiki/Barnacle_Goose, it seems that this practice was banned by Innocent III at the Fourth Lateran Council in 1215.
Seasonality of Food in the Middle Ages
Agricultural production tied to the seasons also had a huge impact on what food was available. For instance fruit was fresher in the autumn, and around harvest-time (August/September). Bread would also be more plentiful because of the availability of cereals after the harvest. In fact it could be argued that the autumn saw a glut of food becoming available. Animals were often slaughtered before the winter began, traditionally at Martinmass (11 November), to avoid the expense of having to provide feed for them over the winter. They might either be eaten then or salted for consumption over the winter. Vegetables would of course also be available subject to the best season for their production.
The way food was prepared is also influenced by the season, with meat often being roasted communally out of doors during the summer when it was too hot to cook over an open fire in an enclosed indoor space, but boiled inside during winter, when the process of boiling would be more suitable for older meat.
Fish was more plentiful during the summer months when the seas were calmer and allowed for more fishing to take place. Again much produce would be salted to allow for year round consumption.
Mortimer, Ian, The Time Traveller’s Guide to Medieval England (London, 2009), p167-168
Whittock, Martyn, A Brief History of Life in the Middle Ages (London, 2009), p182