Mackie soon began creating togs for some of the various divas who would make his name, most notably Carol Burnett and Diana Ross. His glamorous ideas for "Diana Ross and the Supremes and the Temptations on Broadway" (1969) won him another Emmy, and he became the primary creative force behind the costumes for the long-running "The Carol Burnett Show" (CBS, 1967-78). For the next several decades, Burnett would be Mackie's most loyal customer; he did work for her feature "Chu Chu and the Philly Flash" (1981), many TV shows ("Fresno" 1986, "Plaza Suite" 1987, "Julie and Carol: Together Again" 1989), and her later short-lived variety series, "Carol & Company" (1990-91) and "The Carol Burnett Show" (1991). He also provided Burnett's costumes for her return to Broadway in "Moon Over Buffalo" in 1995. For Burnett, Mackie designed both outlandish outfits suited to her engagingly broad comic skits (notably, the green curtain dress complete with rods for the "Gone With the Wind" spoof) and the sequined, floor-length, slit-skirted gowns she so often wore in her famous chats with the audience.

Mackie's next major client was Cher, and his omnipresent penchant for both the campy and the sexy really came to the fore. Some of his spiky creations for the lanky singer-actress were downright glamour punk in style, and Mackie's unabashed outrageousness would later suit Madonna ("The 63rd Annual Academy Awards" 1991), Bette Midler ("Gypsy" 1993) and many other stars eager to be sensuous, bizarre or both simultaneously.

Mackie won more Emmys designing clothes for Mitzi Gaynor's 70s song and dance fests on TV, and he won Oscar nominations for the features "Lady Sings with Blues" (1972, with Ross), "Funny Lady" (1975) and "Pennies from Heaven" (1981). Mackie has also designed for the stage for the likes of Carol Channing ("Lorelei" 1974) and Alexis Smith ("Platinum" 1978) and took a stab and producing and libretto writing for the staging of "Movie Star" (1982).