[dons historian hat]
No army was supplied solely by foraging, to my knowledge. Even as far back as Xenophon, armies had logistical tails. Richard Lionheart kept his Crusaders near the coast so they could be provisioned by ships in the Mediterranean.
Rations were supplemented to a greater or lesser extent by foraging. English troops during the Hundred Years War were well provided with food supplies although foraging came later. Joan of Arc, uniquely among medieval commanders, prohibited her men from foraging. Armies foraged, at the farthest, 60 miles from their lines of march. Within each unit, a mounted group of soldiers would ride forth to steal all the food they could find and defeat any opposition to their quest. As a result, a medieval army would create a path of wasteland of 10 or more miles in its wake. Because of the time invested in foraging, this method of logistics would slow the army’s progress to 5 to 10 miles a day. In enemy territory, looting and pillaging was seen as part of the damage inflicted upon the enemy. In friendly territory, a general would sometimes send ahead a herald to tell residents to provide a certain amount of food and fodder at a designated place and time. In return, the army’s soldiers would not be allowed to forage. With good management, a town could support an army equal to its population for a week or two without undue hardship.
Armies and Warfare in the Middle Ages: The English Experience has a chapter on logistics. Wheat is the most-mentioned foodstuff, followed by malt, oats, beans, peas, cheese, oxen, sheep, pigs, bacon (salt pork), herring, cod, salmon and stockfish. Meat also went on the hoof. Francisco Vasquez de Coronado's expedition into the American South West drove not only cattle but sheep and pigs along the trail. The numbers of the animals were closely tallied. ("Medieval" is a tough nut to crack. There are stories, but not a lot of data. Once we get into the Early Modern era, proper records start to appear.)
The preferred beast of burden was the ox, which was not only eaten, but also pulled the great wagons loaded with arms, provisions, and the parts for siege engines. Cows were kept since they produced milk which was turned into butter and cheese as well as new cows. A live cow was worth far more than the meat on its bones. This was convenient for resupply, but it also slowed the army's march considerably. Slaughtering animals takes time. It also contributed to hygiene issues, as the distribution of the fresh meat to the men took a considerable amount of time, and by the time it actually reached the men the quality was poor. Add in the lack of proper disposal for the carcasses and you have a fairly foul situation.
Bread was the primary constituent in "rations," almost invariably (since Roman times) some form of hard-tack. Hard-tack is simply bread baked until most if not all moisture is removed, which makes it last a long time, sometimes years. It is nearly impossible to actually eat without moistening it in broth or beer. The most common meal would be stockfish or salt pork mentioned above, boiled with beans or peas, and the hard-tack dipped in to soften it enough that it could be eaten. This would be accompanied with cheese and table beer/ale, as well as whatever fresh vegetables were to hand.
Bread and cheese were the staples, as they were easy to carry as personal supplies when the army outpaced its logistical train or the tactical situation dictated different routes of march. A veteran New Model Army officer wrote, "In the late wars both Ireland and Scotland were conquered by timely provision of Cheshire cheese and biscuit."
In the English Civil War, the official ration (at one point) for soldiers on the march was two pounds of bread, one pound of meat and and one bottle (ration) of wine or two of small (weak) beer. Popham's Regiment of Foot, which numbered about 100 men during August 1644, received a daily average of:
Bread & Biscuit: 10.5 oz.; Salt: 1/17th pint; Peas: 3 oz. dried (6 oz. cooked); Beer (weak): half a pint; Meat & Dairy Products: 5 oz.
Rations when in garrison were different. Between January and June 1645, the two hundred Parliamentarians stationed at Chalfield House,Wiltshire ate:
40000 lbs beef
1600 lbs bacon
580 lbs pork
1900 lbs mutton
64 lbs veal
That works out to roughly 1.25 pounds of meat per man per day. They also ate:
15000 pints of wheat
27000 pints of oats
20000 pints of malt
5000 pints of beans
5000 pints of peas
It is dangerous to use English Civil War ration data, however, except where circumstances of supply are known, because ECW armies on the march did not usually expect to supply themselves to any great extent. Rather, householders were expected to billet soldiers at a set rate in exchange for an IOU that often as not was never paid. They were expected to provide food and ale and fodder for horses. The cost to England of free quarter was enormous. In Cheshire £120,000 of free quarter was said never to have been reimbursed, not to mention the claims of villages in the same county which lost as much as £190,000 worth of goods and livestock in plunder. To bring that into perspective, that's £659,097,197 in 2016 £ Sterling, or almost a
billion $USD.
Anyway, those are my pre-coffee thoughts.

Hope you find them helpful.
Cheers,
Bob
www.r-p-davis.com