Bonnie Posselli was born in Lake City, Utah. She earned a degree in illustration from a technical college in 1982, but did not pursue commercial art, preferring to paint landscapes in the plein-air style, focusing on the effects of light. A plein-air painter and western regionalist, her work focuses on her emotional response to Main Street America, agrarian scenes, and forests. She lives in Salt Lake City.

Posselli joined the Plein-Air Society, led by brothers Ken and Dan Baxter. She studied under Alvin Gittins at the University of Utah . She earned a degree in illustration from a technical college in 1982, but did not pursue commercial art as a profession, preferring to paint landscapes in the Plein-Air style, focusing on the effects of light.

San Rafael Swell and Old Town Park City are some examples of her work. In 2002, Posselli was selected by Springville Museum of Art as one of its top painters, and in 2001 and 2003 she was selected to participate in the Plein-Air Painters of America Exhibition on Santa Catalina Island.