WESTON—Once upon a time Judy Garland and Mickey Rooney only had to see a barn to start shouting “let’s put on a show!”

The Weston Playhouse, set to open a $6.3 million second stage and community center beside the silos of the nearby Walker Farm, needed a little more help.

Vermont’s oldest professional theater company is celebrating its 80th anniversary of presenting annual summer bills of Broadway titles and talent. But as the nonprofit arts organization expands its drama education and development programs, it also wants to extend its calendar. That’s why it will cut the ribbon this coming weekend on a 140-seat supplemental facility on nearby Route 100.

“We’re going to continue to perform in the playhouse — that’s still our flagship — but this allows us to do other programs and incubate new work,” managing director Lesley Koenig says.

Weston will keep major warm-weather productions in the historic white-pillared theater on the town green.

But the 300-seat hall is too expansive and expensive to operate in colder months, and so the playhouse staff has spent the past decade working to raise the money to add the new year-round facility at the nearby five-acre farm.

“We have at least a dozen different ways to set up seats and risers, so we can have a student matinee, concert, lecture, meeting, banquet, wedding, circus or sound stage, whatever you want to do,” Koenig says. “Think of all the community programming that can go in there.”

Founded in 1937, the company has evolved over the past eight decades. In 1952, it upended a 15-year history of drama only for something unprecedented: a musical (“Brigadoon”). In 1962, its original home was felled by fire. In 1988, the staff of the rebuilt playhouse reorganized into a nonprofit Equity company.

The Walker Farm project — featuring an 8,000-square-foot barn-like structure designed and constructed by the Breadloaf Corporation of Middlebury in conjunction with theatrical consultants Fisher Dachs Associates of New York — first sprouted as an idea some 15 years ago and as a capital campaign in 2007.

Then came the one-two punch of 2008’s “Great Recession” and 2011’s Tropical Storm Irene, which flooded a $700,000 renovation of the main playhouse’s dressing rooms, prop shop and orchestra pit harboring a baby grand piano.

Weston is inviting the public to a grand opening celebration Saturday at 2 p.m. that will feature Walker Farm tours, food and entertainment, followed by a week-long run of “Joe Iconis and Family,” a concert by a prominent New York based composer and his most frequent collaborators.

The company then will move on to raise the last $2.3 million of a $13 million capital campaign to pay not only for the new building but also for a $1.5 million “Fund for the American Theatre,” $1 million in improvements to the main playhouse and $500,000 for an education endowment for students and interns.

Weston also must replace its longtime leadership trio of producing artistic director Steve Stettler and founding colleagues Malcolm Ewen and Tim Fort, who have announced they’ll retire after the 2018 season, which marks their 30th year of management.

But Weston retains a stable of capable hands, starting with Koenig, who served as a stage director at the Metropolitan Opera at age 23 before going on to earn master’s degrees in business administration and education and taking management positions at the Met, San Francisco Ballet and Opera Boston.

“This completely flexible state-of-the-art space is one of the most exciting things I’ve ever worked on,” Koenig says of the Walker Farm project. “We’re optimistic it’s going to be a magnet for all sorts of activity that will help raise the economy of this whole area.”