Raiders general manager Reggie McKenzie confirmed the trade Monday. Oakland will now have three first-round picks in 2019 after also getting the Chicago Bears' selection in last month's Khalil Mack trade.
"I got a call from [Cowboys vice president] Stephen Jones this morning, he put it on the table, what he wanted to do, and he wanted the player, and he gave me the pick, and that's what it came down to," McKenzie said.
Cooper, the fourth overall pick in the 2015 draft, has 22 catches for 280 yards and a touchdown in six games this season. He opened his career with back-to-back 1,000-yard seasons and made the Pro Bowl twice, but his numbers have fallen the past two seasons.
"I hate to see good players go, but I was on the practice field when Reggie came to me and said the Cowboys would do this for a No. 1 and I said, 'Let's do it,'" Raiders coach Jon Gruden told ESPN's Chris Mortensen. "We're going to try to build this thing the right way. We now have five No. 1 picks in the next two years, so I'm excited about that."
McKenzie said there had been interest in the 24-year-old Cooper from multiple teams this season, but he was holding out for an offer of a first-round pick, which the Cowboys delivered.
"I think he's a first-round player, that's why I had to get that first-round pick," McKenzie said. "Now, has he been inconsistent? Absolutely. But, has he shown greatness? Absolutely. The consistency is something that I'm sure he's worked on, and this guy's still a young player. I think he's going to do well down in Dallas."
The 3-4 Cowboys had been doing their due diligence on receivers leading into the trade deadline and had zeroed in on Cooper, who became available in recent weeks with the Raiders' 1-5 start in the first season of Gruden's second stint as head coach.
The Cowboys entered the season hoping a committee of receivers could make up the production lost when Dez Bryant was released in the offseason. They attempted to sign Sammy Watkins in free agency, but he opted to join the Kansas City Chiefs. The Cowboys drafted Michael Gallup in the third round and added veterans Tavon Austin, Allen Hurns and Deonte Thompson to a group that included Cole Beasley and Terrance Williams.
The Cowboys placed Williams on injured reserve with a foot injury Oct. 6. Last week, Williams was suspended for three games for violating the NFL's substance abuse policy.
Veteran Brice Butler, who was signed Sept. 18, was released Monday to make room for Cooper on the roster.
The passing game has struggled for most of the season, ranking 29th in the NFL. Beasley leads the Cowboys with 33 catches for 350 yards and two touchdowns; no other wide receiver has more than 13 catches.
Gallup caught a 49-yard touchdown pass in Sunday's loss to Washington and has 10 catches for 190 yards. Hurns has 13 catches for 158 yards and had his most productive game of the season against the Redskins with five catches for 74 yards.
Austin has been the big-play threat, with seven catches for 130 yards and two touchdowns, but he is expected to miss multiple weeks with a groin injury.
The last time the Cowboys made a major in-season trade for a wide receiver was in 2008, when they acquired Roy Williams and a seventh-round pick from the Detroit Lions for their first-, third- and sixth-round picks.
Williams did not live up to the expectations after the trade, topping out at 38 catches for 596 yards and seven touchdowns in 2009. The Cowboys released Williams after the 2010 season.
Cooper is set to play 2019 under a fifth-year option worth roughly $13.9 million.
Salary-cap space will not be an issue for the Cowboys, although they want to re-sign leading pass-rusher DeMarcus Lawrence, cornerback Byron Jones and can look at long-term deals for Ezekiel Elliott and Prescott as early as this offseason.
If Cooper provides Prescott, who is signed through 2019, with the outside threat the Cowboys have lacked this season, the quarterback's chances of landing a big deal would increase.
Cooper is in the NFL's concussion protocol after suffering the injury Oct. 14 in Oakland's loss to Seattle in London.