Lea Michele "Hooking Up" With Glee Costar Cory Monteith!

Credit: AP Photo/Charles Sykes

Undercover lovers no more!

After months of downplaying romance rumors, Glee stars Lea Michele, 25, and Cory Monteith, 29, have finally gone public with their relationship, multiple insiders confirm in the new issue of Us Weekly (on stands Friday).

"They've been hooking up for awhile," an insider says of the actors, whose characters were about to get married when Glee's February 21 episode ended.

On February 25, Monteith took Michele to his Vancouver hometown for a romantic sightseeing weekend. "They stayed in a hotel, toured Grouse Mountain and went for sushi and sake," a source reveals.

Adds the first insider: "It's starting to seem a little more serious."

For much more on the Glee costar's hot new romance -- including their intimate date at Il Covo in L.A. on Valentine's Day -- pick up the new issue of Us Weekly, on stands Friday!