From the ahevents.org page:
Battle of Britain 2006 (September, 2006)
Operation Downfall (July, 2006)
Stalin's Fourth (April, 2006)
Fire Over Malta (November, 2005)
Coral Sea (April, 2005)
Rangoon, '42 (October, 2004)
Battle of Britain 2004 (August, 2004)
Brooke's personal scenario page also lists BOB 2004 as the earliest AH scenario he participated in.
What was before BOB'04? It hasn't been until the past few years that I ever paid attention to anything SEA related. I've been around since AH1 came out, but never took notice until BOB'04 (as I recall, I wanted to participate, but couldn't). I vaguely seem to recall stuff went on before that, but what?