n. — Food, Prairies, especially Saskatchewan
a dessert square consisting of an oatmeal or pastry base, date filling and crumble topping.
Type: 1. Origin — Outside of the Prairies, a matrimonial cake is usually called a date square. The term appears to have originated in Canada, and is most frequent in Canada (see Chart 1), where Saskatchewan (see Chart 2) stands out, though it can be considered a Prairie term since Albert and Manitoba also show sizeable frequencies.
See also COD-2, s.v. "matrimonial cake", which is marked "Cdn (Prairies)", and OED-3, s.v. "matrimonial cake", which is marked "Canad.".
Images:

Chart 1: Internet Domain Search, 15 Aug. 2012 -_5_Jul_2013.JPG)
Chart 2: Regional Domain Search, 5 Jul. 2013