They proved they can win a game without injured quarterback Tony Romo.
They proved they can finish strong in the fourth quarter and win a close game.
Both were issues last year when the Cowboys were 4-12.
They were 1-11 without Romo, who missed 12 games with a fractured collarbone, and they lost seven games in which they were within a score in the fourth quarter.
The Cowboys then dropped the season opener against the New York Giants, 20-19.
Unflappable rookie Dak Prescott showed why the days of the Cowboys flailing around at quarterback without Romo are over with a coming of age performance to earn his first NFL victory.
"It was just excitement," said Prescott, a rookie fourth round pick who is starting the first six games of the season because Romo is out with a fractured bone in his back. "I wanted to scream, jump up and down and all around. I was just excited to get that first win."
Prescott completed 22 of 30 passes for 292 yards and scored his first NFL touchdown on a six yard run.
But it was the cool and poised Prescott who drove the Cowboys 80 yards in 11 plays for the go-ahead score with 4:49 left in the game.
"He did an outstanding job in that situation," coach Jason Garrett said. "He just handles things with poise and composure. He gives us a chance to execute ball plays because the demeanor he plays with is infectious throughout our team. Guys see that and respond to that."
But this was not just about Prescott's rise as Romo's replacement.
This was a huge turning point for a Dallas team and a maligned defense which kept the Cowboys in the game and helped seal the victory with repeated stops in the second half.
A failed Hail Mary by Redskins quarterback Kirk Cousins on the final play of the game evened the Cowboys record at 1-1 and prevented them from being in the dreaded 0-2 hole with both losses in the division to start the season.
But it was actually five consecutive stops on the defense that keyed the victory.
Before the Hail Mary, linebacker Justin Durant turned the Redskins back on 4th and 1 at the two-minute warning by deflecting a pass intended for Pierre Garcon.
"It was major," Durant said. "90 percent of the time team's that go 0-2 you don't make it. You can feel the air in the locker room. Guys are feeling good about it. Competitive greatness is finishing well in times of adversity and that was definitely a time for us to make a play."
The Cowboys defense came up with play after play in the second half when it mattered most, which belied their struggles for much of the first three quarters.
The biggest play was an interception by safety Barry Church with the Cowboys trailing 23-20, setting up the game-winning touchdown drive.
"This loss would have torn us apart," defensive tackle Tyrone Crawford said. "We definitely needed this. It would have torn us apart mentally. Now we can relax."