Full disclosure -- I looked it up since I was not sure other than it was at least 2004 or earlier.
And turns out it is actually a trick question, as before 2012 the SEC had divisional regular season champions, but not a single regular season champion for the whole conference similar to the Big XII.
If we look at UK not winning at least a piece of its division crown before 2005, the answer would be 1999.
That season KU came in second behind Texas in the Big XII, while Tennessee won the SEC East, with UK second.
"Travel is fatal to prejudice, bigotry and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime." - Mark Twain "Innocents Abroad"
