The free-agent wide receiver joins a high-powered offense led by quarterback Matthew Stafford and adds to a depth chart at the position that already includes Cooper Kupp, Robert Woods and Van Jefferson.
Beckham became a free agent when he cleared waivers on Tuesday after being released by the Cleveland Browns.
Stafford said Thursday he has a lot of respect for Beckham, whom he played with at a Pro Bowl. He lauded Beckham for being "outstanding" both when the ball is in the air and after the catch and said he was "excited" to be able to work with him on the Rams.
"It's an opportunity for us as a team, it's an opportunity for him to come in here and prove himself to us. What our room is about in the receiver room is pretty special. I know he'll fit right in and continue to get better and hopefully help us as a team," Stafford said.
Stafford said if Beckham wants to win, "that's what we're all about," and he was confident he'll be able to contribute.
"Everybody on our team carves out their role. They do a great job of figuring out what that role is going to be and going out there and proving it both on the practice field and in games, and given the opportunities I know he'll do the same," he said.
Beckham is the second high-profile player added by the Rams this month, after Los Angeles traded for star pass-rusher Von Miller before the deadline last week. Miller welcomed Beckham to Los Angeles on his Instagram Story, posting: "Let's chase this ring family!!!!"
Von Miller and OBJ looking for a ring with the Rams. pic.twitter.com/Qau2RDNgXk— Lindsey Thiry (@LindseyThiry) November 11, 2021
Beckham was also welcomed to L.A. by Lakers superstar LeBron James, one of his good friends, who tweeted: "Welcome to LA my brother @obj ! It's GO TIME!!"
The Rams lead the NFL in total offense this season behind a potent passing attack led by Stafford, who is first in the NFL with 2,771 passing yards. Kupp is the team's No. 1 receiver and leads the NFL in receptions (74), receiving yards (1,019) and touchdown receptions (10).
The Browns excused Beckham from practice last week while the sides negotiated his exit. He had asked to be traded and never developed an on-field connection with Browns quarterback Baker Mayfield. Beckham essentially forced his release last week when his father shared an 11-minute video on social media -- hours before the trade deadline -- of plays in which Mayfield didn't pass him the ball.
"We're all working for the same goal,'' Woods said. "His thing is, I feel like, why he left -- he wanted to be a part of it and contribute, and I think just coming into this offense, he wants to work and contribute. We're all working toward the same goal: winning, grinding. I don't think it should be anything disruptive.''
The three-time Pro Bowl selection has 17 catches for 232 yards and zero touchdowns in six games this season. Beckham had 1,035 receiving yards in 2019, his first season with Cleveland, but suffered a season-ending knee injury in 2020. He has passed the 1,000-yard receiving mark five times in his career.
Browns safety John Johnson III, who spent the past four seasons with the Rams, was on a Zoom call with Cleveland reporters when the news of Beckham's signing broke. Johnson wondered how OBJ will fit in L.A.
"They had a good thing going, like a complete offense," Johnson said. "I don't know. I just feel, like, from being in L.A., I know for a fact the offense runs through Cooper Kupp; even in the run game, the pass game, the screen game, it kind of runs through Cooper Kupp. So obviously, Odell's a big name and he's going to want that attention as well. It will be interesting.
"Coach [Sean] McVay, he's one of the best doing it. He'll find a way to get it done, but right off the bat, I really wouldn't want to go there if I were him. But we'll see how it goes, and I wish him the best.''
The Rams have been remarkably successful at managing the egos and needs of their elite players, with McVay assuaging almost all public disenchantment with the organization. Cornerback Jalen Ramsey was considered a potential locker room problem after he forced his way out of Jacksonville, but he has been a model citizen and a clear team leader in Los Angeles since arriving in 2019.
The Rams (7-2) play the San Francisco 49ers (3-5) on Monday night.
ESPN's Adam Schefter and The Associated Press contributed to this report.