She worked as an entomologist at the American Museum of Natural History (AMNH) in New York for 43 years, writing, illustrating, and creating large models of insects.

[2] While still in high school she knew she wanted to work at the American Museum of Natural History, and called its Insects and Spiders Department to ask about employment.

Based on the advice she received from then-chairman, Frank E. Lutz, she applied to and attended Cornell University, studying biology and entomology, and training in scientific illustration.

She wrote for museum publications, constructed many of the department's displays, built large models, and illustrated entomology handouts still used as of 2016[update].

In addition to working inside the museum, she brought insects and spiders out to New York public schools, presenting in classrooms and eventually earning the nickname "Bug Lady" through her outreach efforts.

[2] In 1964, when both the editor and art director of that magazine left their positions, Gray filled in for both, first as a temporary measure and later on a permanent basis.

[5] She gained international recognition for her work developing models, writing books, and generally supporting the paperfolding community.

Its name changed to OrigamiUSA when Oppenheimer died in 1992, and it remains the largest origami organization in the United States.

When it caught the attention of the Trustee Exhibition Committee, the AMNH Holiday Origami Tree became an annual tradition, still active as of 2016[update].