Is 1 avacodo, some slices of onion , and a handful of garbanzo beans a healthy lunch?

Yes-but not everyday: This sounds like a very healthy lunch! garbanzo beans are a good source of protein & fiber, avocados contain healthy oils & all 3 are rich in a wide array of beneficial phytonutrients. But variety is the spice of life; i advise eating foods of every color as the different colors are made by different nutrients, so don't eat this every day. See http://www.Whfoods.Com/foodstoc.Php for more on these.