Tatabánya is not a foodie destination, but you can eat well on a budget. The traditional Hungarian dishes — gulyás, paprikás csirke, stuffed cabbage — are reliably done at the few family-run restaurants in Bánhida and around Fő tér in the centre.
For something more substantial, the small town of Tata, about 15 km north, has a much better restaurant scene and a famous coffee-house tradition. It is worth the short drive for an evening meal if you have time.