It was a beautiful spring Saturday around noon, and the actress Julianne Moore was spending it at Dia Beacon, the art museum in New York’s Hudson Valley.

“I’ve never been here. Isn’t that crazy?” Ms. Moore said. “We have a house in Long Island — Montauk — and there is that thing in New York, where you go to Long Island or you go upstate.”

When asked if she felt like she was betraying the Hamptons, she laughed: “Don’t tell them I’m here.”

Ms. Moore was in one of the museum’s vast, natural light-filled, industrial exhibition spaces, for the Dia Art Foundation’s spring benefit, which was also a 50th-anniversary party. She was walking around a bleacher-like structure named “Arena” from the artist Rita McBride. (Earlier naked dancers moved around it during a performance called “Momentum.”)

The daytime fete, raised more than $1.5 million, and drew around 600 people. The crowd included the artist and filmmaker Steve McQueen, whose installation “Bass” just opened at the museum; the actresses Frances McDormand and Chloë Sevigny; and the N.F.L. commissioner Roger Goodell.

The event, sponsored by Bottega Veneta, honored six artists including Félix González-Torres, Maren Hassinger, Mary Heilmann, Meg Webster, Mr. McQueen and Ms. McBride, and included a mix of actors, collectors, philanthropists, and other art-world fixtures.

Joan Jonas, the artist whose work is currently on display in a retrospective at the Museum of Modern Art, said she was struck by the size of this year’s benefit.

Reflecting on previous shows she had at the museum, she added, “There are so many more people here now.”

Some guests were there to look at art. “We love Dia,” said Ms. Sevigny, who attended with her husband. “We arrived late, so we’re going to have to look at the exhibits after lunch. The anticipation is building.”

Others made the trip for the people-watching. “There is this airiness and freshness about seeing everybody in the spring light,” said Sara Zewde, the landscape architect who is creating an eight-acre garden outside the museum that is currently under construction. “It’s magical. Everybody is sprinkling and shining.”

The festivities opened with a cocktail reception with breakfast treats like Bloody Marys and candied bacon. Guests then took their seats for a family-style lunch of roasted chicken and grilled artichokes, punctuated by speeches from museum supporters and staff. The day concluded with a dessert reception, featuring sprinkled doughnuts and macaroons.

Mr. Goodell, whose wife is on the board of the museum, mingled with people around the room. “I really enjoy talking to this many artists,” he said. “It’s fun to see how many of them are also sports fans.”