Is it Haram to offer food on marriage day (Nikah)?
It is not Haram to offer food on the wedding day or any other day. One may offer food, one may not offer food. This is not something binding in Sunnah but it is not Haram, it is cultural. It is totally okay to eat as long as the food is Halal, the earning of the person who offered this food has no Haram in it, but it is not Haram as long as the food is Halal and the environment is okay.