Leonard would return to Vel's Parnelli Jones again in 1970, working with famed chief mechanic George Bignotti. In his first race of the year, the Indianapolis 500 he would drive the #15 Johnny Lightning PJ Colt-Ford. In the race Leonard qualified in 18th place and was soon running in 2nd place to teammate Unser. Leonard's engine would quit after 73 laps and he could only finish in 24th place. It was discovered post race the engine switch had been flipped, meaning that there was nothing wrong with the engine and that Leonard could have continued. Leonard would then compete in the Rex Mays Classic at Wisconsin State Fairgrounds Park Speedway where he only led the final nine laps on his way to his first victory since 1965 at Milwaukee. Leonard would start one more race that year, the California 500 at Ontario Motor Speedway, where he would qualify in 6th place and would finish in 13th place after spinning out. Leonard would finish out the season 32nd in points.