The diet was indeed varied, 1.4 kg bread, 0.45 kg meat, 1 l wine and 5 cl oil per day was a minimum according to Goldsworthy (1996, 291). He won't mention where he gets his information from however.
It is however true that food based on grain was more popular than other types of food, even meat. (I reckon that there is one ancient source mentioning that the soldiers revolted when they were out of grain and had to live on meat only for some time, something which could be miss-used in vegetarian propaganda - I cannot leave a reference to this though.)