Within two hours, they voted to reconsider, a move that could undo the first vote.
The proposed amendment would define marriage as between one man and one woman and would ban future gay marriages. If it makes it on the ballot and residents approve it, the constitutional amendment would leave Massachusetts' existing same-sex marriages intact but ban any new ones.
Sixty-one lawmakers voted in favor of advancing the measure, which would appear on the ballot in 2008 and declare marriage to be only between a man and a woman. The proposal still needs approval of the next legislative session.
After the initial vote, gay marriage supporters called for an hour recess, reports AP.
They returned and voted 117-75 to reconsider the vote after a scolding from one of the Legislature's most outspoken gay marriage opponents, Democratic state Rep. Philip Travis, who said lawmakers neglected their constitutional duties.
"You are running from your responsibility on this question. You know it. Your conscience knows it," Travis said.