Trenary placed 5th in her first senior national championships in 1986. Later that summer she won the U.S. Olympic Festival. In fall 1986 she placed second to Elizabeth Manley at the St. Ivel International. At the U.S. championships in 1987, she finished second in both the compulsory figures and short program, where she landed a triple flip jump for the first time in her combination. In the long program Trenary landed four clean triple jumps, including the triple flip, and she upset reigning world champion Debi Thomas to take her first senior national title. At the 1987 World Championships, she rallied from 11th in the compulsory figures to place fourth in the short program, again landing the triple flip jump in combination, and fifth in the long program, to place 7th overall. In 1988, Thomas regained the U.S. title, with Trenary finishing second. Trenary placed 4th at the 1988 Winter Olympics. She was 5th at the 1988 World Championships, where she fell on the triple flip in both her short and long programs. Due to her strength in compulsory figures, Trenary again won the U.S. Championships in 1989, although she was defeated by Kristi Yamaguchi in the free skating. Trenary won bronze at the 1989 World Championships.