Expand region increases the selected region by semantic units. Just keep pressing the 'C-=' key until it selects what you want. The notion of "semantic" is language-sensitive.

Example: editing

(setq alphabet-start "abc def")

With the cursor at the `c`, it starts by marking the entire word `abc`, then expand to the contents of the quotes `abc def`, then to the entire quote `"abc def"`, then to the contents of the sexp `setq alphabet-start "abc def"` and finally to the entire sexp.