Credit or Debit Card in Restaurants?

Not all restuarants accept Credit card

there are few who accept neither
please check before you dine

If a restaurant does accept credit cards they will for sure accept debit cards (Bancontact/Maestro). Not always the other way around.

The simple answer is that it varies.

Many restaurants will accept both Bancontact/Maestro and at least Visa and Mastercard credit cards, although in both cases there are likely to be minimum value sale restrictions and some cards issued outside Belgium may be unacceptable.

Other restaurants will accept EITHER Bancontact/Maestro OR Visa and Mastercard credit cards, normally cheaper establishments the former and more expensive establishments the latter.

A few restaurants will accept only cash and, perhaps oddly, these establishments tend to be at either extreme of the price range. They will, however, almost certainly be able to tell you where the nearest cash point is, and, in extremis, even allow you to go and get the necessary cash (after having seen your eID).

The golden rule has to be to look for the appropriate "accepted/not accepted here" signs and, if they are not visible, to ask.

Yes. Just about everywhere accepts bancontact/maestro. Credit cards are not as widely accepted.

I'll admit that my experience specifically in Brussels is very limited however, in the country at large and with the exception of fast food/burger places, I have not found bancontact commonly accepted though credit cards generally are.

I've never found a restaurant that will take bancontact, only the odd sandwich/takeaway/cafe shop.