Typography LATIN SMALL LETTER O WITH MACRON

I saw a letter that I needed to added to a document (an "o" with a line across the top) but didn't know how to type it in. So I opened the Font window and found the letter in the characters palette. I was hoping it would show me a magic key combination like using OPTION "e" then "e" to produce "é". But it gave me nothing. I could add it to favorites, I could double click it and get this "ō" inserted in the document. But I'd like to know how to get it into the document without opening the Fonts windows and palettes. Is there a way to find out that information within Lion system?