The moves address two of Oakland's most glaring needs, with Harris expected to fill a void at one of two tackle vacancies, and Walker projected as a replacement for departed veteran Jerry Porter.
The signings came at a steep price for players deemed expendable by their former teams. Walker, 29, received a six-year contract that includes $16 million in guarantees and a $12 million payout in 2008. Harris, who turns 26 on March 15, signed a three-year, $14 million deal.
The signings were confirmed by two members of the Raiders front office who requested anonymity.
Harris, 6-foot-7 and 322 pounds, started every game for the 49ers in 2005 and 2006 but appeared in only 12 games as a reserve last season after losing his starting job to rookie Joe Staley in training camp. His contract expired at the end of last season, and the 49ers didn't try to re-sign him.
Walker caught 26 passes for 287 yards and no touchdowns in eight games for the Denver Broncos in 2007. He missed eight games with a right knee injury and struggled in the games he played. He began the season with back-to-back 100-yard games. Soon thereafter, he underwent a third operation on his right knee.
The Broncos reportedly attempted to trade Walker but didn't receive any takers. Therefore, they released him Friday to avoid paying a $5.4 million roster bonus that was scheduled to kick in Tuesday.
He is expected to play opposite Ronald Curry in an offense that lacks any other proven receivers.
Harris will be given an opportunity to replace either Barry Sims at left tackle or Cornell Green on the right side.
In other news, the Raiders freed up $4.1 million in salary-cap room when the retirement of defensive tackle Warren Sapp was made official Monday. Sapp had three years left on his contract when he retired in January.
Also, the Raiders freed up $4 million or so by restructuring the contract of left guard Robert Gallery. His cap number was just under $7 million for 2008.
Finally, former Raiders defensive end Tyler Brayton signed a two-year contract with the Carolina Panthers. He voided his contract after last season.
Contact Steve Corkran at firstname.lastname@example.org.