Peters is entering the fifth and final season of his rookie contract.
"Been really pleased with Marcus," McVay said. "And especially pleased with what you could find out with all the experiences we went through in one year."
The Rams acquired Peters, 26, last year in a trade with the Kansas City Chiefs in exchange for a 2018 fourth-round and 2019 second-round pick. In three seasons in Kansas City, Peters intercepted a league-best 19 passes, was a two-time Pro Bowl selection and one-time All-Pro.
But he played inconsistently throughout the first half of the Rams' 13-3 season, and allowed several explosive plays, including a 72-yard touchdown pass to New Orleans Saints receiver Michael Thomas in the Rams' first loss of the season in Week 9.
"He made plays that weren't really indicative of what we feel like he is," McVay said. "What I love the most is he took accountability for it."
By later in the season, and following some adjustments from defensive coordinator Wade Phillips, Peters settled in. He finished the regular season with three interceptions and eight pass deflections before he went on to perform well throughout the playoffs, and had arguably his "best game," McVay said, in a loss to the New England Patriots in Super Bowl LIII.
"If he keeps playing this way," McVay said, "hopefully we'll get a chance to work together for a long time."