Via The Buffy Trivia Guide:
Howard Gordon co-wrote the episode What’s My Line? (Part 1) with Marti Noxon, and was consulting producer on the show. He was also a consulting producer and writer on Angel. He wrote the Angel episodes ‘Hero’, ‘Expecting’ and ‘The Ring’. Howard worked with Buffy’s executive producer David Greenwalt before, on an episode of The X-Files. He wrote many episodes and was co-executive producer of both 24 and The X-Files.
He was also a consulting producer for 'The Inside' and will be working with David Fury on the next season of '24' as well.