Osgood spent three years at FCS Cal Poly before transferring to play for the San Diego State Aztecs football team. In his sophomore year at Cal Poly, Kassim led the nation in receiving yards, ranked second in receiving yards per game, and sixth in catches per game. That year, he also set an NCAA Division I-AA record with 376 yards receiving in a game against Northern Iowa and set school records for both touchdowns in a season and catches in a game. Prior to the 2001-02 college football season, Osgood transferred to San Diego State University where he would be named first-team All-Mountain West Conference. In that year he ranked second in the nation in catches and fourth in nation in yards per game. He and teammate J. R. Tolver combined to set NCAA records for receiving yards in a season by teammates with 3,337 yards and catches with 236. Kassim earned his degree in Sociology from San Diego State.
Professional career
San Diego Chargers
Osgood was signed by the San Diego Chargers as an undrafted free agent ahead of the 2003 NFL season. He saw some playing time in his first two seasons with the team, appearing in all 16 games and catching two touchdown passes each season. Prior to the 2006 season, he signed a four-year extension and assumed he would become a bigger part of the offense. However, that did not happen. Osgood expressed frustration with his role in San Diego and remarked "I'm going to be a great receiver some day – probably not in San Diego". Osgood was named as a member of the 2007 Pro Bowl, 2008 Pro Bowl, and 2010 Pro Bowl squads, each time as the AFC special teams representative.
Jacksonville Jaguars
On March 6, 2010, Osgood signed with the Jacksonville Jaguars to a three-year, $6.675 million contract, with a $2.2 million signing bonus. Osgood was released by the Jaguars on March 13, 2012.
Detroit Lions
The Detroit Lions signed Osgood on August 22, 2012
The San Francisco49ers signed Osgood on June 4, 2013, but he did not make the regular season roster. He was re-signed on September 11, 2013. He completed the 2013 season with the 49ers having played 14 games where he registered 12 special teams tackles, one blocked punt and recovered one muffed punt for a touchdown. Osgood was re-signed to a one-year contract with the 49ers on March 17, 2014, for special teams and a worthy back up receiver. The 49ers released him on August 30, 2014 as part of the final roster reduction to 53-players. On September 2, 2014 the 49ers re-signed Osgood to a one-year contract. However, on September 6, 2014 the 49ers released Osgood again. He was yet again re-signed on September 8 when LaMichael James was cut, He was released on October 8 to make room for the signing of safetyBubba Ventrone. Then on October 10, the 49ers cut quarterbackJosh Johnson to make room for him on the 53-man roster once again. Osgood was placed on injured reserve after suffering a broken hand injury during a 7-17 49ers loss to the Seattle Seahawks.
Personal life
In 2007, Osgood made a cameo appearance as a Marine in the first-season finale of the CBS drama Jericho.