For the most part, I only wrote high-level documents. I didn't write any of the plot-critical characters and I didn't do detailed area development or implementation.
I wrote our RDC (Region Design Constraints) documents, which had a basic overview of the concepts/conflicts for all of the primary locations (e.g. Goodsprings, Mojave Outpost, the vaults, The Strip, Nellis AFB, etc.) and I did the initial write-ups for the companions (just a page each covering their basic concept, background, personality, voice, and intended plot arc).
Let me just do a mini-writing credits dump to answer a lot of common questions here. Most of the major plot characters (Benny, Victor, Caesar, Mr. House) and the main story itself were written by the game's creative lead, John Gonzalez. Eric Fenstermaker wrote Veronica and Boone. Chris Avellone wrote Cass, Lanius, and Oliver. Travis Stout wrote Lily and Raul. Most of the other characters, major and minor, were split between the writers above and other area designers. Of course the actual full design treatments, quests, and implementation of areas were done by the area designers.
The only "big" characters I wrote were Chief Hanlon, Arcade Gannon, and President Kimball's speech. Also I just wrote/structured the dialogue in GECK. The design, implementation, and scripting for the associated quests of those dialogues (Return to Sender, For Auld Lang Syne, You'll Know It When You See It/Arizona Killer) were handled by Matt McLean, Travis Stout, Jeff Husges, and Charlie "Master of Hoover" Staples.
Most of the content design and generation I did was for game systems (SPECIAL + gambling/Caravan + equipment).
