By the 1970s, HGA was recognized as one of the most innovative design firms in the Midwest. With architects, engineers, and other specialists working side by side, the office exemplified the interdisciplinary tradition of Walter Gropius and the Bauhaus that the founders learned from their own teachers and mentors. In the early 1970s, Curt Green designed the extraordinary O'Shaughnessey Auditorium for the College of St. Catherine in St. Paul. As part of an arts district that included Green's design for a new studio arts building, the concert hall became the symbol of the campus and a home for the Minnesota Orchestra and other groups.

A national AIA award winner in 1977, the New Melleray Abbey in Dubuque, Iowa, marked a collaboration between Ted Butler and liturgical consultant Frank Kacmarcik in renovating and exposing the masonry wall and timber trusses of the Abbey Chapel. At Hamline University, HGA designed the Bush Memorial Library and the Alumni Learning Center that restored a historic building and created a graceful connection to a modern open learning space. Perhaps, the most memorable project of the 1970s is Orchestra Hall in Minneapolis. Designed in conjunction with HHPA of New York, HGA served as architect of record for this new home for the Minnesota Orchestra, considered one of the finest concert halls in the world.

HGA's founders believed it important to begin to diversify the practice of the firm so the organization would continue to grow and provide more career growth opportunities for staff. They began this process with the hiring of recognized experts in the healthcare planning and design field. At this time, a strategic alliance with The Architect's Collaborative of Cambridge, Massachusetts, led to the design of the original phases of the Health Sciences complex at the University of Minnesota. Subsequently, an alliance with the large healthcare design firm, HDR, of Omaha, led to selection for design of the prestigious Minneapolis VA Medical Center. HGA also served Rochester's Mayo Clinic during the firm's early days of its healthcare practice and it has continued to serve this world renowned healthcare clinic over the years.