Here's three from my own childhood (3 older brothers somehow came up with these...) Anybody else know any good ones?
"Good food, good meat, good God let's eat!"
"Rub-a-dub-dub, hurray for the grub, yay God"
and the perpetual fave...
"Father, Son and Holy Ghost, who eats the fastest eats the most!"
(Thanks to Robert for the technical spelling assist)