She returned to BYU and served as the associate chair, the chair of Design & Technology, and the resident costume designer for the school's Department of Theatre & Media Arts.
During her 30 years at BYU Swenson designed over 250 productions, including musicals, operas, Shakespearean presentations, and film. For over 20 years she also designed for BYU's international touring group, The Young Ambassadors. Professionally, Janet served 15 years as resident designer at Robert Redford's Sundance Theatre and has designed at the Tony Award-winning Utah Shakespearean Festival for nineteen seasons, including the festival's 50th anniversary productions. Other professional credits include work for the Disney Channel (Velveteen Rabbit), the Pacific Conservatory of the Performing Arts (1776), the Idaho Shakespeare Festival, PTTP at the University of Wisconsin, the Tuacahn Center for the Performing Arts, and the Skylight Opera Theatre in Milwaukee. She has also designed many summer productions in Wyoming at both the Pink Garter Theatre and Jackson Hole Playhouse.Swenson worked closely with Harold I. Hansen and was involved in the production of the Hill Cumorah Pageant, where she helped to create the original look of the pageant during its formative years.
Professor Swenson taught courses in costume design as well as supervising and teaching in the TMA department's extensive makeup program. She is the recipient of many awards, including the prestigious Karl G. Maeser Award for Creativity in 1996 and the Kennedy Center’s Excellence in Education Award from the 2012 Region VIII Kennedy Center American College Theatre Festival (KCACTF). Her most challenging project was designing and supervising construction of 2,500 costumes for the LDS Church's production of Light of the World, which played to sold-out audiences in LDS Conference Center during the 2002 Olympics. She is a member of the International Alliance of Theatrical Stage Employees, the American Federation of Television and Radio Artists, the United States Institute for Theatre Technology, and the Utah Council of the Arts, and is the National Archivist for Theta Alpha Phi.
Swenson retired from BYU in 2012, but during her time at BYU she had been responsible for the design of many productions, including The Phantom of the Opera and White Christmas. In 2013 Swenson received special recognition at the SCERA's annual "Evening of Stars" gala for her significant contributions to art. She also designed Mary Poppins at Tuacahn for the 2013 season.
- The Universe - A Night of Stars: BYU faculty awarded for contribution to the arts (27 Feb 2013)
- The Daily Herald - Star struck: SCERA smiles on local arts with special honors (21 Feb 2013)
- The Universe - The creation of a character (20 Oct 2011)