The deal comes two days after Chicago re-signed Grossman to a one-year contract and said he would compete for the starting quarterback job with Orton.
In three seasons, Orton is 12-6 as a starter and has the fourth-highest winning percentage among Bears quarterbacks with at least 16 starts since 1961. He spent most of last season as the third-stringer behind Grossman and Brian Griese, and had mixed results while starting the final three games.
Orton was 43 of 80 with 478 yards, three touchdowns and two interceptions. The Bears won two of three, but finished a disappointing 7-9 after winning the NFC championship the previous year.
Grossman, who started the Super Bowl after an up-and-down season in 2006, struggled again early last year and was benched following the third game. He returned for five more games before injuring his left knee.
Grossman passed for 913 yards with three touchdowns and one interception for an 80.2 passer rating when he returned. That was an improvement over the first three games, when his 45.2 rating with one TD and six interceptions contributed to a 1-2 start.
The Bears have been busy lately.
They agreed to a a two-year extension that runs through the 2010 season with tight end Desmon Clark on Sunday. Last week, they gave defensive end Alex Brown a two-year contract extension while letting former Pro Bowl wide receiver Muhsin Muhammad, veteran offensive tackle Fred Miller and defensive tackle Darwin Walker go.