He is best known for his role as Donald Maltby on Brothers, and as Ted Nichols on Open House, which he worked on with his current wife, Alison La Placa.
That same year, MacKenzie was cast in the pilot of a series proposed for NBC's 1980 fall schedule, The Six O'Clock Follies, a period piece set in 1967 Saigon.
Making the Grade was also the first series role for actor George Wendt, with whom MacKenzie worked later that year when he did a guest appearance on "Coach's Daughter", an episode of NBC's Cheers.
He appeared as Ted Nichols, a real estate mogul who proposes a business partnership with snobbish yuppie Linda Phillips (played by his current real-life wife, series regular Alison La Placa).
Upon the cancelation of Duet, La Placa and MacKenzie's characters were spun off into its sequel comedy series Open House, which centered on Linda and Ted's new venture in real estate.
Midway through the 1990-91 season, MacKenzie joined the cast of ABC's Miller/Boyett sitcom Going Places as talk show producer Arnie Ross.