View Single Post
There may be such an option, but I don't know of it. I would contact Omni directly (posting to forum is not equivalent) and ask if such a thing exists.

If not, the following trivial Automator action can be saved as an application and placed in the dock. Dropping an OPML file on the application icon will cause OmniOutliner to open the file and set the font size to 16. Unfortunately, you'll still have to bring OmniOutliner to the front.

RobTrew is the original author of the script included (in modified form).