Peaceable Tate wondered what they ate in the Old World before the discovery of the New World. An interesting question.
Here, courtesy of the internet, is a partial answer.
Foods That Originated in the Old World: apples, beets, broccoli, carrots, cattle (beef), cauliflower, celery, cheese, cherries, chickens, chickpeas, cinnamon, coffee, cucumbers, eggplant, garlic, ginger, goats, grapes, honey (honey bees), lemons, lettuce, limes, oats, okra, olives, onions, oranges, pasta, peaches, pears, peas, pigs, radishes, rice, sheep, spinach, tea, watermelon, wheat. Plus lots of fish and seafoods
We know what they ate on the Mayflower and in their first year at Plymouth because Edward Winslow, a passenger, described it in his diary. On board the ship they ate dried and salted meats and fish, dried fruits, hard cheeses, gruel, and hardtack which was dipped in broth to make it soft enough to eat. They had pease porridge hot and cold - this is rather like split pea soup. They had hens, ducks, and geese on the Mayflower, so they probably had eggs and ultimately, chicken, duck and goose. They also had goats, so they had goat milk and cheese.
They did not have cow milk, fresh cheese from cows, butter or cream until 1624 when cows were brought from England.
By the first Thanksgiving, they had received a lot of help from the Native Americans so the meal included some New World foods: They had:
From the Ocean: cod fish, lobster, clams, seals, and eels
From the Land: wild turkey, duck rabbit, deer, partridge, goose, eagles, plums, pumpkins (stewed or fried) wild grapes, beans, onions, lettuce, carrots and leeks. They also had wheat flour and Indian corn. Also walnuts, acorns, dried currants and chestnuts.
My source said they had olive oil - I'd have to hear more about that before I believed it. It could be true of course, but... it seems odd as it was sold in Chemists Shops and considered medicinal in Britain until after WWII, as far as I know.
We also know what the Roman legionnaires ate because of studies done of bones found in Roman cemetaries (as well as written records). Their diet was mostly grain: wheat, barley, and oats, and also spelt and rye. They were given an amount equal to 3.5 pounds of grain per day. Each of them carried their own little frying pan to make their own bread or porridge. They probably also carried preserved meat - early versions of prosciutto, speck, bresaola and sopresso etc. They also foraged as they went, for meat and fish mostly.
They ate less meat than grain, but when they ate meat it was ox, sheep, goat, pig, deer, boar, and hare, in most places and in some areas, elk, wolf, fox, badger, beaver, bear, vole, ibex, and otter. Broken beef bones suggest the extraction of marrow for soup. Alongside the animal bones, archaeologists found equipment for roasting and boiling the meat as well as for making cheese from the milk of domesticated animals. Fish and poultry were also popular, the latter especially for the sick.
And wines, beer, ale, mead, hard cider or other fermented beverages were what everyone drank, even kids. Water was too dangerous. Men in early America also drank rum and gin as a beverage with meals.