We usually read her story, "I Stand Here Ironing," in my ENGL 103 course at Drexel. She does some interesting things with point of view, pacing, time. I don't know her work beyond that story. Perhaps the NY Times article is accurate -- seems so. But I find it a shame for a writer to be reduced to an -ism. Though some writers maybe invite the reduction. Still, with the best writers, summing them up as a "feminist," or a "post-colonialist," or any other -ist, should be insufficent. We apply -isms all of the time, a shorthand way of grouping and categorizing, but no one really thinks that "modernist," for example, really captures Henry James, or "absurdist," Franz Kafka, I hope. I haven't read enough of her writing to know whether Olsen's work transcends the -ism and whether mentioning her next to James is remotely justified.
Clarification: The NY Times did not mention her next to James. I did (in the post above), but not intending it as a comparison or a measure of literary quality, which I think is clear, but maybe this clarification will succeed in obscuring it. You see how I can go on and on about nothing when I'm trying to avoid working on a syllabus? It's quite a skill.