Eating options at Volubilis itself are limited to the small café beside the ticket office, which serves mint tea, cold drinks, and a simple tagine. The food is unremarkable but the shaded terrace is a welcome refuge from the midday sun.
For a proper meal, Moulay Idriss is four kilometres away and has a handful of small restaurants serving Moroccan staples — harira, tagine, couscous on Fridays — at very reasonable prices. The town gets relatively few tourists compared with Fès or Meknès, and eating there has a pleasantly unhurried quality.
Most visitors who arrive on a grand taxi from Meknès combine Volubilis and Moulay Idriss in a single half-day trip and eat lunch in Moulay Idriss before heading back. If you are based in Meknès, the medina there has a much wider choice of restaurants for the evening.