Did they have grocery stores in the Middle Ages? No, of course not. A medieval person transported by time machine to a modern grocery store would be stunned. It would be far beyond their most ambitious visions of miraculous plenty.
And yet we walk through such stores ourselves without giving it a second thought. We get irritated at a wobbly wheel on a cart and don't even act amazed that strawberries are available year round, strawberries easily ten times the size of medieval strawberries.
(This strawberry is actually mutant, several berries that grew together. Local strawberries, available only a few weeks a year, are stunningly better than those shipped in from great distances. But strawberries never used to be available more than a few weeks a year.)
Medieval people generally grew their own food or bought it at the equivalent of a farmer's market. A forward-looking city council would stockpile grain in case of a shortage. "Farm to table! Eat local!" Everything old is new again. The principal foods that one would buy in a store were bread and beer. A bakery and a brewery were indeed often combined (see more here on beer in the Middle Ages). A good sized town might also have a butcher, though most people ate little meat most of the year.
Inns would however sell prepared foods, at a higher price of course. Their principal customers were travelers and people from out of town. There was nothing like the modern fast-food place where people would stop to pick up a burger or chicken nuggets on the way home from work.
So next time you're in a grocery store, which has, literally, tens of thousands of different products (think about how many kinds of cereal, how many kinds of salsa, how many types of pickles, and I'm just getting started), imagine yourself with a medieval person. He or she will be awe-struck.
Click here for more on what medieval people ate.