Mark McCormack helped Tarkenton invest, making him wealthy enough to "retire this week if wanted to", as "New York" magazine wrote in 1971. Tarkenton was a pioneer in computer software, and founder of Tarkenton Software, a program generator company. He toured the United States promoting CASE or "computer-aided software engineering" with Albert F. Case, Jr. of Nastec Corporation, but ultimately merged his software firm with James Martin's KnowledgeWare, of which Tarkenton was president until selling the company to Sterling Software in 1994.