How much meat was in a Legionary\'s diet?

[Epictetus]

I would imagine that it differed with the location, but this example is interesting:

A small room in a wooden building in the castellum of Alphen aan den Rijn, The Netherlands, was suspected to have been a centurion's latrine. Pollen and seed analyses of ground samples, taken from in and around this room, showed the presence of many edible plants, mainly wheat, but also several fruits, spices, oil seeds, nuts, etc., mixed with weeds growing in cultivated fields. The grain was infested with a grain weevil. Besides plant products, oysters, mussels and some freshwater fish were found.

Here is the full article: Diet of a Roman centurion at Alphen aan den Rijn, The Netherlands, in the first century AD.

Then there is this oft-cited example:

So the army suffered from the utmost difficulty in its corn-supply, because of the indigence of the Boii, the apathy of the Aedui, and the burning of the homesteads – so much so that for several days the troops were without corn, and staved off the extremity of famine by driving in cattle from the more distant hamlets. Yet never a word was heard from their lips unworthy of the dignity of Rome and of their previous victories.

Caesar, Gallic War, 7.17

I have often seen this given as an example of the soldiers not wanting to eat meat, but unless the Latin can be read differently, I don’t get that impression. Caesar mentions capturing cattle many times throughout the book – probably more than a dozen, based upon a quick word search – and there are no hints of dissatisfaction from the soldiers.

I would guess they ate what was readily available, and what was most often available was grain.