Can you clarify on which orthodox church? Greek, Russian and Ethiopian all come to mind, but I'm not aware of a general middle eastern one (genuinely curious). Perhaps it wasn't called orthodox back then (prior to 300AD)?

Presumably the Eastern Orthodox Church which includes the Greek and Russsian branches and was centered in Constantinople/Istanbul.

Oriental Orthodox Churches: https://en.wikipedia.org/wiki/Oriental_Orthodox_Churches

Are probably the most "Middle Eastern", but apparently they, Eastern Orthodoxy, and Catholicism were all the same church until various splits happened, so I'm not sure if you can say any of them are "older".

The Orthodox churches really just get to trace their lineage to their respective founding apostle. If we do assume that the apostles that had to travel the least from Jerusalem were the ones whose churches started first, then Syria and Egypt (Coptic) were probably the first. Granted, we're making a big assumption.

When the splits are that old we call them "schisms" :-)