[3][4] In 1964, McCollum moved to Essex, England, pursuing the idea of being an actor, and joined a local theater group in Southend-on-Sea, but he changed his mind about a career in theater and returned to California in 1965, moved into a small mobile home park in Venice Beach, California,[5] and attended Los Angeles Trade Technical College for five months, attempting to learn the trade of restaurant management and industrial kitchen work.

For two years, he worked for Trans World Airlines at the Los Angeles International Airport, preparing meals for flights but, in 1967, he decided to educate himself as an artist.

He learned quickly, influenced initially by reading the writings of the Fluxus artists and the early structuralists, and found a job as a truck driver and crate-builder for an art handling company in West Hollywood.

During the late 1960s, McCollum produced his early work while living in small rented storefront spaces, first in Venice Beach, and later in Santa Monica.

[7] McCollum has had over 140 solo exhibitions, including retrospectives at the Musée d'Art Moderne in Lille, France (1998), the Sprengel Museum in Hannover, Germany (1995–96), the Serpentine Gallery in London (1990); the Rooseum Center for Contemporary Art in Malmo, Sweden (1990), IVAM Centre del Carme in Valencia, Spain (1990); Stedelijk Van Abbemuseum in Eindhoven, The Netherlands (1989) and Portikus in Frankfurt, Germany (1988).

He is known for utilizing the methods of mass production in his work in many different ways, often creating thousands of objects that, while produced in large quantity, are each unique.

"[9] The system involves organizing a basic vocabulary of 300 "parts" which can be combined in over 30 billion different ways, created as "vector files" in a computer drawing program.

McCollum has used the system in collaborations with a community library, schoolchildren, home craftworkers, writers, architects and other artists, as the Shapes are created to be used for many different kinds of projects, and so far have been produced in the form of both prints and sculpture, in Plexiglas, Corian, plywood, hardwoods, metals, rubber and fabric, in a variety of sizes.

He has also written texts and interviewed fellow artists for books and catalogs, including Matt Mullican (1979 and 2006)[12] Allen Ruppersberg (1999),[13] Andrea Zittel (2001),[14] Roxy Paine (2002),[15] and Harrell Fletcher (2005).