The boss takes a hostile, domineering attitude towards George from the moment they first meet. He asks a lot of questions, but his main purpose seems to be ti assert the fact that he is the boss. Part of the interview goes as follows:
"Why'd you quit in Weed?"
"Job was done," said George promptly.
"What kinda job?"
"We . . . we was diggin' a cesspool."
"All right. But don't try to put nothing over, 'cause you can't get away with nothing. I seen wise guys before. Go on out with the grain teams after dinner. They're pickin' up barley at the threshing machine. Go out with Slim's team."
The boss only appears in one scene. This is in Chapter 2 when George and Lennie first arrive. Steinbeck apparently didn't want to develop him as a character, probably because he wanted to focus on the employees. Curley, as the boss's son, is a sufficient representative of authority. He seems to be trying to imitate his father's bullying manner, but he can't quite carry it off because most of the men do not respect him.
The fact that George answers "promptly" when the boss asks why they quit in Weed shows that George was expecting that question and had the answer rehearsed. George is sensitive about the real reason for their leaving Weed and wants to dismiss the subject as quickly as possible.
The "dinner" the boss is referring to has to be the noon meal, since Steinbeck indicates that it is ten in the morning when they arrive at the ranch. It was customary for farmers to eat the biggest meal at around noon in order to fortify themselves with calories for a hard afternoon's work. Nowadays many people consider "dinner" to be the evening meal. The word "supper" is disappearing from common usage. It used to mean a light evening meal.
One of the reasons that Steinbeck chose to place the Weed incident so far away from the Salinas Valley would appear to be that it would make it impossible for the boss to do any checking up on George and Lennie. No doubt Lennie's transgression with the girl in Weed is known all over Siskiyou County by this time.