Embed External Website into my Website

I have been doing some research on iframes's in Wordpress. On a non-multisite, I can use iFrames no problem. However, on my multisite, I can not use iFrames due to security issues. I tried with my Super Admin account to add the iframe into the subsite's page, but that does not work either.

I have read the WPMUDEV Blog post on oEmbed, but that process seems too complicated for long lists of sites.

I really need to be able to allow embeds on my Multisite. Any ideas?