A complete meal in 19th century Europe, and, in the pre-20th century West broadly speaking, is one that included bread. Bread--made from wheat, barley, rye, or some combination thereof--was the core of the European diet. In the 19th century, consumption was something like 4 lbs. per person per week; adult males ate nearly a pound of bread per day. You can see the deep history of bread's central roles across the longue duree in a range of sources. In the Epic of Gilgamesh, dating from the third millennium BCE, the harlot Shamhat civilizes the wild man Enkidu in part by seducing him sexually, but then she offers him bread and beer. He turns his head at these things, but she persists, enjoining him to "Eat the bread, essential to life... drink the ale, the lot of the land." Bread consumption marked the difference between civilization and barbarism for them. Another example is the Lord' Prayer, which asks to "Give us this day our daily bread." In this case, the same pattern obtains: bread is a synecdoche for "food" or "material sustenance," so that "bread" is like the deepest, most basic, "core" food.

Of course, leavened bread is not always available, and in those cases we see a range of other, primarily vegetable products. If we're talking, say, 18th-century Europe, then we might build out from bread with various porridge-like meals, such as oatmeal, furmenty, or groats. Beans and peas were common legumes, grown during the early modern period as part of crop rotations, and hence regularly consumed. Root vegetables were also a major component of diets, including potatoes but also turnips, swedes, onions, carrots, and more. These had the advantage of being durable, easily storable without much processing, and they could even be left in the ground if necessary.

Aside from meat, we do see a range of animal products, primarily cheese. Eggs, for whatever reason, don't show up in the records nearly as much, though we know people kept chickens. And butter or some kind of drippings were considered an essential additive to bread in northern Europe (olive oil was more common in the Mediterranean).

Really, though, if you're asking a peasant or an urban laborer what's for dinner before 1900, the answer is most likely to be bread.

See Drummond and Wilbraham's The Englishman's Food; Burnett, Plenty and Want; Rubel, Bread; Sidney Mintz's Sweetness and Power is a history of sugar, but includes a discussion of the anthropological work on bread as the central, food-defining food.