The international players are familiar to first-year Lions head coach Jeff Tedford, who coached both at the University of California.
After college, Morrah played 27 games for the Seattle Seahawks from 2009 to 2011, finishing with 16 receptions for 194 yards. After being released by Seattle, the 28-year-old had brief stints with San Francisco, Detroit and Denver.
Bigelow attended the Tampa Bay Buccaneers training camp last season after four years at Cal under Tedford.
The 22-year-old rushed for 877 yards on 155 carries with five touchdowns during his time with the Golden Bears. He added 42 receptions for 305 yards and was also a special teams' threat with 1,363 yards on 62 kickoff returns.
Morrah and Bigelow join former Cal receiver Lavelle Hawkins on the Lions' roster after the 28-year-old signed with the team last month.