Romo, who injured his back for the third time in the last 18 months nearly two weeks ago, sat out last week's loss to the Arizona Cardinals and skipped the team's first practice in London on Wednesday. But he participated in drills on Thursday and again on Friday.
"He looked pretty comfortable to me," Cowboys coach Jason Garrett, who spoke before Friday's practice, said of Thursday's session. "Clearly, he wanted to get the blood flowing through his body and get his movement back both in the pocket and also throwing the football, and he had a pretty good day yesterday."
The Cowboys (6-3) play the Jacksonville Jaguars (1-8) at Wembley Stadium on Sunday in the last of three regular-season games in London this year. They have lost their last two games, however, with backup Brandon Weeden playing last weekend.
Romo has fractures in two small bones in his back. The injury is unrelated to a herniated disk last year or to off-season surgery to remove a cyst earlier in 2013.
The quarterback said Thursday he was still a little sore, but called it "normal stuff," and said his back loosened up during practice.
Garrett, however, still hasn't made a decision on who will start on Sunday.
"We'll take today, we'll see how he feels after yesterday's work," Garrett said, "and hopefully he can practice the way we need him to practice today and just take it right up until game time."
The Cowboys have played overseas nine times in their history, including twice in London. But this is the first time they'll be playing a regular-season game outside the United States.
Most of the teams that have made the journey to London over the years have praised the team-building aspect of such a long trip to a foreign country, and some have taken the time to catch some of the local sights.
Dallas plans to do a little of both on Friday.
"We're going to go to the Tower of London and see the Crown Jewels," Garrett said, "and I think the players are excited to do it."