Schobert, a six-year veteran who had worked out for the Broncos earlier in training camp, has started 80 games in his career with the Cleveland Browns, Jacksonville Jaguars and Pittsburgh Steelers, who released him in March.
Last season, he started 16 games at inside linebacker, finishing with 112 tackles, an interception and a forced fumble. He had a 144-tackle season for the Browns in 2017 and has five seasons of 100 or more tackles, including the past four.
"Schobert is another experienced guy that we know we can put in there and can play right away,'' Broncos coach Nathaniel Hackett said Monday. "He can bring that leadership. He's had lots of years with hundreds of tackles and he's a guy who's played special teams''
Also Monday, the Broncos formally activated both outside linebacker Randy Gregory (shoulder) and offensive tackle Billy Turner (knee) from the physically unable to perform (PUP) list. Neither player had participated in the Broncos' offseason program or in training camp to this point.
Gregory underwent surgery to repair his right rotator cuff shortly after choosing Denver over Dallas in free agency and signing a five-year, $70 million contract.
"It's something I'd been dealing with for two, maybe three years,'' said Gregory, who's coming off a six-sack season in his final year in Dallas. "I'd been playing with it for so long, I kind of wanted to fight through it. But I think for the long term it was better for me and for the team.''
Gregory said "the plan'' is he will be in the lineup for season opener Sept. 12 Seattle.
"(The shoulder injury) was something I've been dealing with for two, maybe three years now,'' Gregory said. "And it got to the point where it was hindering my play ... I feel confident ... (Monday) is a big day for me.''
With Griffith's injury, the Broncos, who had already moved Baron Browning to outside linebacker in the offseason, were thin at inside linebacker. Browning started nine games at inside linebacker last season. Griffith dislocated his left elbow on the defense's second play of the game Saturday against the Dallas Cowboys.
Griffith, who was acquired in a trade with the San Francisco 49ers last season to provide special teams help, had worked his way up the depth chart into the starting defense. Griffith started four games last season and had worked with the starters much of the time in the offseason program and so far in training camp.
Alex Singleton played in Griffith's spot against the Cowboys after Griffith's injury. Singleton, who was signed in free agency this offseason, played 37 snaps and finished with four tackles.
Hackett told reporters Monday that Griffith is expected to be sidelined for four to six weeks.
Singleton led the Philadelphia Eagles in tackles last season.
The Associated Press contributed to this report.