I have data and systems protected by a firewall.

I have data and systems protected by a firewall. There is web content data I want other to see outside of our firewall but I do not want a web server on the protected side of the firewall. Can I use a web OPC server in the DMZ to pass on the web data to an unprotected web server?

You will have a/some computer(s) outside the firewall, possibly (a) OPC Server computer and (b) Webserver, or have them both combined in the same computer.

As that is the situation, the answer here would be "yes", this would work without a problem as far as the OPC Server data being made available to the web-server.