Suspended all of last season and reinstated only a matter of days before training camp started, Gregory played in 10 first-half snaps in Saturday's 21-13 loss to the Cincinnati Bengals at AT&T Stadium.
"I haven't played an actual game in basically two years," said Gregory, who did not record a tackle or pressure. "Practice is one thing. Conditioning's one thing. Personal training's one thing, but actually going out there and be with my guys and at least attempt to make some plays, it felt real good."
The Cowboys took Gregory in the second round of the 2015 draft despite the off-the-field concerns that saw his draft stock take a hit. After a strong start in the preseason, an ankle injury kept him out of four games, and he did not record a sack in the 12 games he played. He has one sack in his career.
Gregory has played in only two of the past 32 regular-season games because of multiple violations of the NFL's substance-abuse policy. He opened training camp on the non-football injury list, as the Cowboys wanted him to work on his conditioning after such a long absence.
He took part in just four full practices during the Cowboys' time in Oxnard, California, but quickly showed that he was ready for at least some preseason action. In one practice, he recorded two sacks in a three-play span.
"Once we saw him practice, we anticipated him being able to play this game," coach Jason Garrett said. "Certainly we want him to play the whole time. We want to be deliberate with him, and he went through all the steps we wanted him to go through."
After the final practice on Thursday in Oxnard, Gregory said he does not feel like he has made the 53-man roster yet. Gregory said he hopes to play more Aug. 26 against the Arizona Cardinals.
Gregory said he was not reflective about his journey back to the Cowboys before kickoff.
"I think if I did that, it would have kind of taken my mindset away from the game," Gregory said. "I think I did it the right way, just coming in here like a professional and get ready, be out there early, warm up and then carry on as I would any other game."
Gregory has impressed his teammates in his comeback.
"It's unbelievable to see what he's overcome, how he's played," linebacker Sean Lee said. "If you watched him in practice this week, it was so fun to see his talent on the football field and his joy for the game. He's worked really hard to get healthy. He's been an inspiration for us, and to see him practice is something very special."