Lyle began his practice in 1972, after completing his studies at the University of Wisconsin Law School. He also became a Certified Public Accountant shortly after beginning his practice. At the time Lyle joined the firm, it was known as Hunter, Madden, Plager & Hasting.
In 1978, Lyle became a partner with the firm, and its name was changed to Hunter, Plager, Hasting & Krug. In 1981, the partners at the firm purchased the German American Insurance building, and rehabilitated it to house the firm offices. The building was rechristened as the Lincoln Douglas Center in honor of the historic Lincoln-Douglas debate.
Throughout his practice Lyle has taken pride in serving families and businesses throughout Northwest Illinois and Southwest Wisconsin focusing on complex tax, estate planning and administration, and related litigation. In recent years he has also provided mentorship for the other attorneys at the firm as they began their practices.
As an active participant in community affairs, Lyle has served on the Board of Directors for Highland Community College Foundation, St. John United Church of Christ Endowment, Chain Link Cyclists, Freeport Aquatic Swim Team, and Monroe Clinic.