If we have an internal list of consumers that do not currently have accounts with us, can we market to them without having the opt-out wording on the letter/marketing material?

You mean past customers? There is no requirement that I know of to provide an opt-out of direct marketing materials that you send to consumers. Many banks maintain such lists for their own customers, but there is no requirement to do so.

Just fyi- make certain if marketing via email they have an "opt out" of future emails and/or unsubscribe.