I suppose where I live they mostly ate food made from grain. Like bread or barley gritz or other tasteless stuff. And then some available vegetables, berries, some animal produce, probably not a cow unless they were rich, more like eggs and occasionally a chicken.

I think the Roman empire also spread quite some culture and food across Europe. But I can't imagine living before the Columbian exchange. That brought us most stuff we eat as if today. Yeah and colonialism in general, that made some goods available for people in Europe.