The extension, which runs from Canoga Park to Chatsworth, will now open to the public June 30. Metro plans to offer free rides that day from 7 a.m. to 7 p.m.
The extension includes new bus platforms at the Canoga Park station and a park-and-ride lot at the Sherman Way station.
It's expected to be busy. The Orange Line already has some 25,000 boardings a day.