John Bowker of the Giants had an extra-base hit in each of his first
three games in the majors, although he didn't get one in his fourth.
The last person I could find who started out with such a stretch was
Joel Hanrahan (a pitcher!) of Washington last year.

Using Baseball-reference.com's Play Index, the only two players with
streaks longer to start their career were Jason Bay (who got traded in
the middle of it and sat out a few months) and Coco Laboy.

Has anybody looked into this relatively arcane record?

Bob Timmermann