Guthrie qualified for and competed in the 1977 Indianapolis 500, in a car entered by Rolla Vollstedt, but finished 29th with engine troubles. She would compete in two more Indy 500s, finishing ninth in the 1978 race while driving with a fractured wrist (injured in a charity tennis event two days earlier) she hid from race officials. Overall, she competed in 11 Indy car events with a best finish of fifth. During her unsuccessful bid to qualify for the 1976 race, many of the drivers in the male-dominated sport stated that the reason she did not qualify was mainly due to her gender. These comments angered then three-time champion A. J. Foyt to the point he lent Guthrie a back-up car to conduct a shake-down test. Her top practice lap in Foyt's car would have been adequate to qualify for the field. She was unable to obtain funding through corporate sponsorship, and was forced into retirement.