Q.  How often can I submit?

A: As often as you want.  Many outlets will not publish the same author more than once every few months.   Also remember, for most op-ed pieces there exists a brief but strong window during which editors would be interested in the topic you discuss. Continuously submitting a piece regarding, say, US and Middle Eastern policies across the spectrum of outlets might not be the best idea, especially if you aren't getting responses from editors. Plan submissions carefully pegged to specific news hook.  Listen carefully to the feedback  (including silence from the editors – which can signal something you're submitting is too far off base).