#Bash, 66 bytes

A=`printf %c {A..Z}`
for i in {0..25};do echo ${A:$i}${A::$i};done

I create a full alphabet in A, then print 26 rotated versions of it by taking the characters beginning at n and appending those preceding position n.

Bash, 66 bytes

A=`printf %c {A..Z}`
for i in {0..25};do echo ${A:$i}${A::$i};done

I create a full alphabet in A, then print 26 rotated versions of it by taking the characters beginning at n and appending those preceding position n.