The Southwest Independent Soccer League hits the outdoors for the first time in the league's history in 1989. The league actually goes by the name Southwest Outdoor Soccer League (SOSL) briefly to differentiate the two leagues.

 

The expansion Colorado Comets join the league and proceed to win the first of several USL championships after dropping just one game in the 12-match season. The second place Tulsa Renegades, 10-2, were upset by Addison in the playoff series two games to one, losing both on penalty kicks. Colorado then defeated the Addison Arrows, 3-1, in the outdoor Final. Colorado nearly swept the honors for the inaugural outdoor season. Ed Eid was named Coach of the Year and Kelvin Norman was the league's Most Valuable Player. Don Gallegos finished first in points and goals, while Chino Melendez finished tied for first in assists with Tulsa's Steve Hayes.

 

The Colorado Comets would go on to repeat as outdoor champions in 1990 in addition to winning the 1990-91 indoor crown, becoming the only team in USL history to win the indoor and outdoor titles in the same year. The Comets then left the league at the end of the 1991 outdoor season, returning in 1998 under new ownership. Former owner Ed Eid's presence remained as the director of communications. The club was renamed the Denver Cougars in 2001 following a change in ownership.

 

The Addison Arrows rebounded during the indoor season, winning the Tex-Ark-Oma Division with the league's fifth best regular season point total. Addison then preceeded to sweep Austin and the Richardson Rockets two games to none in the quarterfinals and semi-finals, respectively. They finished their perfect postseason by knocking off the expansion Phoenix Hearts, the Cactus Division's regular season champion, three games to none in the championship series. Andy Crawford, who played for the Permian Basin Shootin' Stars and Colorado Comets during the 1989-90 season was named the league's Most Valuable Player and Lubbock’s David Swissler was the top goalkeeper for the second consecutive season.