Which preposition to use with helpings

of Occurrences 28%

" "I like to be pestered, ma," said Pearl, as she began on a generous helping of bacon and eggs.

at Occurrences 1%

He followed them home and they treated him well and always gave him a regular helping at meals as if he were a human being and did not merely throw him the scraps as if he were a dog: nor would he have eaten them if they had.

in Occurrences 1%

To John's sharpened perceptions the fact that Carlen was not as usual helping in this labor loomed up into significance.

Which preposition to use with  helpings