Here is a great example of someone that stuck to the program, ate a lot and gained 60 pounds over a year. Check out both threads to see the change from a body weight of 175 lbs to a body weight of 235 lbs. In his first two months on the program he gained 33 lbs and got much stronger.
He ate about 6,000 - 7,000 calories a day including the gallon of milk a day. He stuck religiously to a program designed to increase strength and size - Mark Rippetoe's Starting Strength. He did not change the program at all...he just did what he was told.
To get big you'll have to work hard on getting strong, eating a ton of food and getting a ton of rest.
First two months
After a year