The William L. Pereira & Associates records contain over 400 distinct documents from the corporate archives of the architectural firm, William L. Pereira & Associates. The majority of the collection consists of the firm's project files, which contain architectural plans, materials for presentations to clients, site studies, project workbooks, interim progress reports, executive summaries, feasibility studies, master plans, concept studies, land use projections, long range development plans, and environmental impact statements documenting the majority of the firm's projects from 1960 to 1989. The collection also holds six pre-1960 project documents created under Pereira's earlier firm, Pereira & Luckman. Projects with significant amounts of documentation in the collection include expansions to the Los Angeles International Airport (LAX); long range development plans for the University of California, Irvine; various projects for the Lockheed Corporation and North American Rockwell Corporation; master plans for the University of Missouri; and urban development planning for Burlington Northern Railroad concerning various properties. Records in this collection also document architectural projects that were never built, such as the pyramidal tower for the ABC headquarters in Manhattan.

Aside from the project files, the collection holds a smaller quantity of news clippings, photographic prints (the majority of which were photographed by Julius Shulman), speech transcripts, and audiovisual material about Pereira and the works of William L. Pereira & Associates. This material covers a much larger period of time, spanning 1939 to 1985.

Subsequent to the initial acquisition of the William L. Pereira & Associates records in 1997, the USC Libraries added two accruals of material to the collection in 2021 and 2022. Johnson Fain, a successor firm to William L. Pereira & Associates, donated the 2021 accrual, which consists of additional project files, photographs, and administrative files from the offices of Johnson Fain. Some of the material from the 2021 accrual are branded under "Johnson Fain and Pereira Associates" and "Johnson Fain." Monica Pereira, William L. Pereira's daughter, donated the 2022 accrual, which comprises family correspondence, photographs, drawings by William L. Pereira, and newspaper clippings.