how do I fix the page/post title on the browser tab?

I am trying to figure out how to change the title of the browser tab in IE or Firefox, etc. Screenshot attached.

It says, for example, "Oasis | "
I want it to say "Oasis | Sunroom"

This would be PAGE/POST TITLE | WEBSITE TITLE

I know it is in the header I need to edit, but am not sure what to put there.