This members-only tutorial provides the steps to make iframes placed in Code Block components in Oxygen responsive.
Before:
After:
Step 1
In the Oxygen editor add a Code Block inside a Section.
Add/assign a class called say, iframe-container to the Code Block.
Paste your desired iframe code.
Ex.:
<iframe src="https://oxygenbuilder.com/" style="border:0px #ffffff none;" name="myiFrame" scrolling="yes" frameborder="1" marginheight="0px" marginwidth="0px" height="400px" width="600px" allowfullscreen></iframe>Step 2
Create a new Stylesheet at Manage > Stylesheets and add this code: