Neither quarterback got everything to his liking Saturday night.
At least Tannehill's side left with a victory.
All five of the game's touchdowns came with most of the starters already done for the evening.
"I told the team, a lot of games are going to come down to the fourth quarter," Dolphins coach Joe Philbin said. "And we made some plays in the fourth quarter. Our guys played well in the fourth quarter . hard-earned victory."
Tannehill played into the third quarter, completing 13 of 21 passes for 119 yards. His only big mistake was his final throw, an interception inside the Dallas 10 on Miami's opening possession of the third quarter.
It was the first interception in 41 preseason throws for Tannehill, who is one of the biggest reasons why Miami thinks this could be a breakthrough season.
"You can see the things that we're doing," Dolphins owner Stephen Ross said on the game broadcast. "I'm expecting much better things."
Tannehill also missed on what should have been a 35-yard touchdown pass to Mike Wallace, saying afterward the "miscommunication" on the play was his fault.
"We'll get it," Wallace said.
Romo completed 10 of 18 passes for 87 yards for the Cowboys, and his surgically repaired back got tested plenty of times by the Dolphins' defense -- twice on sacks by Cameron Wake.
"It was good to see Tony out there playing," Dallas coach Jason Garrett said at halftime. "He got knocked around a little bit, and that could be good and bad. ... It's good to have him feel the physical part of the game."
Romo noted there are some things Dallas has to clean up.
"It felt good to get through a half," Romo said. "We want to put more points on the board, but we hurt ourselves with penalties. The game is always going to be hard if you keep putting yourself behind."
Patmon picked off a screen pass from Moore with 7:17 left, reading the play perfectly, but Miami -- playing with no available placekicker because John Potter left with a hip injury -- scored the game's final 14 points.
Another notable good sign for Miami was the preseason debut of Knowshon Moreno, the team's offseason acquisition at running back. He got loose for a 19-yard gain on his first touch of the exhibition schedule. He finished with 64 yards on 10 carries.
"We did some good things," Moreno said.
Miami got the game's first touchdown when Dallas' defense couldn't find a way to stop Damian Williams.
Or Damien Williams, either.
The similarly named Dolphins -- Damien is a running back, Damian is a wide receiver -- paired up to deliver the game's first touchdown. Damien Williams got loose for a 20-yard run, one play before Damian Williams ran under a play-action offering from Moore and hauled in what became a 54-yard gain.
Two plays later, Damien Williams went in from the 1, then added a 2-point conversion.
Dallas DE George Selvie left in the first half with a shoulder injury, but thought afterward it was not serious. . Dolphins LB Koa Misi was among those who did not play for Miami. . Byrd, who played for the Miami Hurricanes, threw up the school's "U" symbol with his hands after catching the TD pass. . Both teams end the preseason at home Thursday, Miami hosting St. Louis, Dallas hosting Denver.
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It took 14 passes before Houston Texans quarterback Brian Hoyer threw an incomplete pass against the New Orleans Saints.
Philip Rivers joined some impressive company Sunday by surpassing 40,000 career passing yards and rising to No. 12 in the all-time passing touchdown rankings.
A late second-quarter pick, which led to a San Diego TD and a 21-9 Chargers halftime lead, extended Blake Bortles' streak -- the longest in the NFL.
The Redskins' defense played one of its best games of the season in the first half, holding the Giants to 117 total yards.
Lions coach Jim Caldwell is keeping an eye on his alma mater during its run to the College Football Playoff.