Rush returns to the spot he held from the 2017-19 seasons.
"I just think he's shown that he can run the complete offense," owner and general manager Jerry Jones said on 105.3 The Fan in Dallas. "Credit to him. He had some tough competition. Those guys didn't cut him any slack. He's had a lot of reps. All of our quarterbacks had because of the absence of Dak. All of those things make us feel real comfortable here."
Rush has thrown three passes in his career and none since 2017. The Cowboys released him in favor of DiNucci a year ago but re-signed him to the practice squad after Prescott suffered a season-ending ankle injury.
In the preseason, Rush completed 29 of 46 passes for 272 yards with two touchdowns and no interceptions. Gilbert threw for 301 yards on 28-of-50 passing with one touchdown and no interceptions. DiNucci completed 35 of 66 passes for 348 yards with two touchdowns and four interceptions.
Gilbert and/or DiNucci could come back to the Cowboys' practice squad.
The Cowboys could look for No. 2 quarterback help based on other team's cuts, but Jones said Rush's experience in the current system is a plus and would make it difficult to trust a newcomer with such a quick turnaround before the Sept. 9 opener against Tampa Bay.
"You've got a pretty high bar here in terms of what's the most effective way to play if you don't have Dak now," Jones said.
As for Prescott, who returned to full practice last week from a latissimus strain in his right shoulder, Jones said he is full go with no limitations.
"He's moving good," Jones said. "He's really got that zip on the ball. We know that he's been throwing with his key receivers for a few days out here the last few practices, and so frankly as far as him being able to execute and execute the throws and move around the way he should against Tampa, I don't have any concern at all about that."