503. Those Who Didn't Eat Bread

Brachos 5:8

Only those who ate at least an olive-sized portion of bread can be counted in a zimmun. If seven ate bread and three ate vegetables or other foods, the three may be counted in the zimmun, so that God's Name may be included in the text. The one who leads the zimmun must be one of the seven who ate bread. If six had bread and four ate vegetables, the four may not be counted toward the zimmun – a clear majority of people who ate bread is required. This is only the case with the zimmun of ten. When it comes to the zimmun of three, each of them must have eaten an olive-sized portion of bread.

Brachos 5:9

Let’s say that two people ate together and finished, then a third person came along and ate. If the others can eat any food together with him, all three may join together for a zimmun. The one who is the greatest Torah scholar among them should lead bentching, even if he only arrived at the end of the meal.