grep 2.5: --only for long line runs forever

[Sven Hartrumpf]

Hi.
"a" is a file with one long line:
> wc a
      1   33330  242456 a

The indended match is at the end of the line:
> fgrep --version
fgrep (GNU grep) 2.5
> fgrep --only "analysis-quality " a
analysis-quality

Very nice and fast. But:

> grep --version
grep (GNU grep) 2.5
> grep --only "analysis-quality " 
runs forever (I stopped after 5 minutes).

Greetings
Sven

P.S.
This is my actual goal (with many more matching lines!):
grep --only "(analysis-quality [^)]*)" big-file # the closing ) comes after 
some characters
Should I use grep? Or something else? sed?