Crayton was traded to the San Diego Chargers for a seventh-round pick in next year's draft. The deal could get upgraded to a sixth-round pick if Crayton catches 40 or more passes in 2010.
He's averaged 38 catches the last two seasons.
"I'm glad that it's over so I can now know what needs to be focused on," Crayton told ESPN 103.3 FM's Galloway and Company. "I'm going to a contender. A legitimate shot to go out there and be the No. 2 and contribute."
The move allows the Cowboys to go younger at the wide receiver position. Second-year player Kevin Ogletree is elevated to the fourth receiver on the depth chart in place of Crayton. Rookie Dez Bryant is the No. 3 behind starters Roy Williams and Miles Austin.
"He got off to a good start last year," team executive Stephen Jones said of Ogletree. "He made some big plays in big games for us. I certainly think his future is bright. Obviously, this does clear the way for him to do more. I'm certain that he'll answer the bell."
Crayton sought a release following April's NFL draft, when the Cowboys selected Bryant in the first round. After missing several voluntary workouts, Crayton returned for the mandatory minicamp saying he wanted to remain with the team. But Crayton also said he wanted a fair opportunity at playing time.
Bryant's development -- he was moved to the first team in three-receiver sets -- raised concerns for Crayton about his ability to remain with the team.
The Cowboys fielded calls from several teams in the last week regarding Crayton's availability. After Thursday's final preseason game, Crayton's agent, Fred Lyles, requested the team release his client. Lyles took a call from San Diego officials and then contacted the Cowboys about a possible trade.
The Chargers appear to be a nice fit for Crayton, because the Cowboys run a version of their offense.
"You know I'm licking my chops about that one," Crayton told ESPNDallas.com's Ben Rogers. "I go from one Pro Bowl quarterback [Tony Romo] to another [Philip Rivers]. One Pro Bowl tight end [Jason Witten] to another [Antonio Gates]. Another dominant defense, a nice, young running back, a good offensive line ... I'm looking forward to it."
Dallas picked up a sixth-round pick for McQuistan, who was a seventh-round pick in 2006. McQuistan, drafted as a tackle, was moved to guard this season. He played in just seven games, with no starts, mainly on special teams.
McQuistan rejoins Dolphins coach Tony Sparano, who was his offensive line coach with the Cowboys in 2006 and 2007.