1980–84

In 1980, at the age of 13, Garrison reached the junior international elite level. She competed at the 1980 U.S. Junior National Championships and won a gold medal on the balance beam. At the USGF International Invitational, she took the bronze on the floor exercise. Two years later, she won the all-around at the 1982 U.S. Olympic Festival in Indianapolis.

Moving up to the senior division in 1983, Garrison finished twelfth at the 1983 U.S. World Trials competition. At the 1983 World Artistic Gymnastics Championships in Budapest, she contributed to the U.S. team's seventh-place finish but did not qualify to any individual event finals.^[6]

In 1984, Garrison competed at the American Classic (finishing ninth) and at the U.S. Classic in Niagara Falls, New York (finishing twelfth).^[7] However, she finished 10th in the U. S. Olympic trials. After several teammates were injured, Garrison moved to second alternate for the 1984 Olympic Team.

1985–87

In 1985, Garrison finished fifth at the Arthur Gander International and was third in the all-around at the Swiss Cup. At the 1985 U.S. National Championships, she won a gold medal on the beam. She placed second at the U.S. World Trials and made the U.S. team for the 1985 World Championships in Montreal. The team finished sixth, and as an individual, she was eighteenth in the all-around competition.^[8]

The following year was less successful for Garrison. She competed at the 1986 Olympic Festival in Houston and placed fourth in the all-around and on the vault, fifth on floor exercise, and sixth on the uneven bars. At the 1986 U.S. National Championships, she placed 39th in the all-around. She also went to a World Cup event in Beijing and placed 13th.

In 1987, she placed fifth in the all-around at the National Championships and made the U.S. teams for the 1987 Pan American Games and the 1987 World Championships. At the Pan American Games, she won gold medals in the team and balance beam competitions and placed third in the all-around. At the World Championships, she contributed to the team's sixth-place finish.

1988

At the 1988 National Championships, Garrison placed second in the all-around, behind Phoebe Mills, and won the gold medal on beam and 3rd on floor. Her finish at Nationals qualified her to the U.S. Olympic Trials in Salt Lake City, where she again placed second behind Mills and secured a spot on the 1988 U.S. Olympic women's gymnastics team.