McGinnis immediately became one of the marquee players of the ABA, playing a key role on the Indiana Pacers' championship teams in each of his first two seasons with his hometown franchise. He was named the ABA Playoffs MVP in 1973, averaging 23.9 points and 12.3 rebounds in 18 playoffs games to help the Pacers repeat as champs. His best season came in 1974-75, when McGinnis scored a career-high 29.8 points per game en route to ABA MVP honors. He nearly averaged a triple-double in the playoffs that year (32.3 points, 15.9 rebounds, and 8.2 assists in 18 games), but the Pacers fell short of the title, losing to Kentucky in the ABA Finals.