C#, 98 bytes

var a="ABCDEFGHIJKLMNOPQRSTUVWXYZ";a+=a;for(int i=0;i<26;i++)Console.WriteLine(a.Substring(i,26)); 

C#, 98 bytes

I have tried to see if I can generate the letters shorter than just initializing them as a string, but it's not really possible. The letters are 26 bytes and this snippet alone

for(char a='A';a<'[';a++) 

is 25 bytes. I think initializing them and then appending them with a+=a is a good solution, but with C# you are limited by the bytecount of functions like Substring() and Console.WriteLine().

My attempt at 98 bytes:

var a="ABCDEFGHIJKLMNOPQRSTUVWXYZ";a+=a;for(int i=0;i<26;i++)Console.WriteLine(a.Substring(i,26));