Jamieson, Fausset and Brown on Leviticus 2:6

6. part it in pieces, and pour oil thereon--Pouring oil on bread is a common practice among Eastern people, who are fond of broken bread dipped in oil, butter, and milk. Oil only was used in the meat offerings, and probably for a symbolic reason. It is evident that these meat offerings were previously prepared by the offerer, and when brought, the priest was to take it from his hands and burn a portion on the altar.