Our Mishna on Amud Beis refers to a custom where they would give out roasted grain at the wedding ceremony of a virgin.  What is the basis and symbolism of this custom?

Abudarham Laws of Blessings Ninth Gate Blessings on Commandments Marriage Blessings, quoting a verse (Tehilim 147:14) השם גבולך שלום חלב חטים ישביעך which equates peace with abundance of plump grain.  Thus, we are wishing upon the marriage peace and harmony, perhaps through financial security.

Similarly, Rashi (Avoda Zara 8b) discusses a custom of planting barley prior to the marriage and then bringing the sprouts to the ceremony.  The implication is that just as barley sprouts quickest from all the other grains, so too this couple should be fruitful and multiply.

As the Gemara (Kerisos 6a) says, simna milsa, signs accomplish things.  We also discussed this theme in Psychology of the Daf (Yevamos 60 and Psychology of the Daf Rosh Hashana 29). Here too, our good wishes for the Chosson and Kallah are prayer through action, hopefully activating blessings for their future.

My thought about the possible source for this custom is that the roasted grain itself a remez to children, as we see two halachos where roasted grain is given to children:

1. Shulkhan Arukh OH 472:16 and Pesachim 108b:  It is a Mitzvah to give the children snacks of nuts and roasted grain on the eve of the Seder so they won’t fall asleep and also ask, “Why is this night different?”
2. Shulkhan Arukh CM 228:18 It is permitted for a storekeeper to distribute snacks of nuts and roast grains so that children, running their parents’ errands, will frequent their store.

Our modern equivalent of this is throwing the candy bags at an aufruf or bavorfen. The actual word, bavorf, means to throw. It’s important to keep in mind that the packages should be constructed in a manner that they don’t break open, and the food inside ruined. Otherwise, it is a violation of bal tashchis (wasting food), as discussed in Shulkhan Arukh OC 171:5 and Mishna Berura 171:21.