1
general::
Pronounce a short prayer before a meal, as in Before we started in on the turkey, we asked Liz to say grace. The word grace here signifies asking for God's blessing or giving thanks for the food being served. [Early 1300s]
American Heritage Idioms
2
general::
Phrase(s): say grace
to say a prayer of gratitude before or after a meal. • Grandfather always says grace at Thanksgiving. • A local preacher said grace at the banquet.
McGrawhill's American Idioms And Phrasal Verbs