Bill Oakley was a writer at The Simpsons from seasons 4-6 and an executive producer/showrunner with his writing partner Josh Weinstein from seasons 7-8.
This was the long process of writing one episode:
1. Work on story ideas. 2 months. Beginning, middle and an end: three acts, ideally including act breaks but doesn’t have to be complete.
2. Present story ideas to everyone. 15-20 minutes to present the story. Everyone else throws in their thoughts and jokes.
3. Writers room. 10-12 people. Go through scene by scene fixing any story problems. 1h – 3 days.
4. Write an outline. Way, way too long – up to an hour of television. ~40 single spaced pages.
5. Show runner gives notes and suggests cuts.
6. Two weeks to write the script. First draft ~62 pages.
7. Rewriters room. A few hours to a few weeks. Go through line by line under direction of show runner. To ~47 pages.
8. Table read.
9. Rewrite. 1-2 days. To ~42 pages.