Is the expression "Say your piece" or "Say your peace"?

Solution 1:

It seems to be say your piece and hold your peace. Because 'peace' and 'piece' are homophones, they are easily confused.

Google Ngram shows piece being 20X more common than peace in 2008, but 45X more common in 1999 (acknowledging the horrendous predictive value of Ngrams). So, in a decade or so... it may well be; not based on the Ngram, but based on how misuse has so often turned into common usage.

Solution 2:

I have always seen "say your piece," as if telling an actor to recite their script.

Other than that, I found that "speak your peace" can be used, but only in a very limited context, where "peace" literally means "peace." The general form uses "piece." This article also mentions that "speak your peace" is usually used as a variant of "hold your peace."

http://wiki.answers.com/Q/Is_it_speak_your_piece_or_speak_your_peace#slide=01&article=Is_it_speak_your_piece_or_speak_your_peace