A.R. Gurney beside a billboard advertising his play “The Perfect Party" in 1986. (Rick Maiman/AP)

A.R. Gurney, who portrayed the fading culture of the Eastern WASP aristocracy in such mordantly comic plays as “The Cocktail Hour” and “Love Letters” and became one of the most widely produced dramatists of his generation, died June 13 at his home in Manhattan. He was 86.

His literary agent, Jonathan Lomma, confirmed the death. The cause was not known.

Mr. Gurney worked for years as a teacher before he found major success in the theater in the 1980s with “The Dining Room,” which was a finalist for the Pulitzer Prize.

Like many of his plays, it examined the furnishings, customs and emotional fragility of upper-middle-class society in vignettes spanning several decades. The play established Mr. Gurney as a major playwright and brought comparisons to the fiction of John Cheever — whose works Mr. Gurney also adapted for the stage.

In the play, a college student brings a camera into the dining room of his aging aunt Harriet, who is pleased to display her crystal and cutlery. Then he explains the anthropological purpose of his visit: “Well, you see, we’re studying the eating habits of various vanishing cultures. For example, someone is talking about the Kikuyus of northern Kenya. And my roommate is doing the Cree Indians of Saskatchewan. And my professor suggested I do a slide show on us.”

A.R. Gurney in 2016. (Mike Pont/Getty Images for American Theater Wing)

“Us?” Harriet says.

“The WASPs,” the nephew replies. “Of the northeastern United States.”

It was a culture Mr. Gurney knew well, as a scion of privilege and tradition in Buffalo, where he, his parents and seven of his eight great-grandparents were born.

“Most of my plays are very close to home,” he told Playbill in 2010. “That was very much my family on stage.”

At a time when many of the characters of other playwrights were cursing and throwing things around the stage, Mr. Gurney found a niche as the decorous adult of the theater, with his intelligent, provocative, bitterly humorous plays.

“As a chronicler of contemporary America’s most unfashionable social stratum — upper-middle-class WASPs,” New York Times drama critic Frank Rich wrote in his review of “The Dining Room,” “this playwright has no current theatrical peer.”

Mr. Gurney became one of the most prolific dramatists of his time, with more than 50 plays to his credit. He sometimes had two plays in production and a third in the works.

A.R. Gurney in 2011. (Jason Kempin/Getty Images for Drama Desk Awar)

With “The Cocktail Hour,” first produced in 1989, Mr. Gurney wrote perhaps his most personal play, about an aspiring playwright, John, who returns home to tell his skeptical parents, Bradley and Ann, that he has written a play called “The Cocktail Hour.”

Bradley: That’s a terrible title . . . To begin with, it’s been used.

John: T hat’s ‘The Cocktail PARTY,’ Pop. That’s T.S. Eliot.

Bradley: Even worse. We walked out on that one.

Ann: This is ‘The Cocktail Hour,’ darling . . . You invite people to a cocktail party. A cocktail hour is family. It’s private. It’s personal. It’s very different.

Bradley: Nobody will know that. It will confuse everyone. They’ll come expecting T.S. Eliot, and they’ll get John. Either way, they’ll want their money back.

Also in 1989, Mr. Gurney premiered perhaps his most widely produced work, “Love Letters,” a two-person play that debuted on Broadway with Colleen Dewhurst and Jason Robards. It focuses on an aging man and woman who read letters written over a period of 50 years, revealing their hopes, regrets and deepest emotional scars.

“Love Letters” received glowing reviews, was a Pulitzer finalist and has been produced on television three times. It has been performed by stars such as Elizabeth Taylor, James Earl Jones, Laura Linney, Julie Harris and William Hurt.

“WASPs do have a culture — traditions, idiosyncrasies, quirks, particular signals and totems we pass on to one another,” Mr. Gurney told The Washington Post in 1982. “But the WASP culture, or at least that aspect of the culture I talk about, is enough in the past so that we can now look at it with some objectivity, smile at it, and even appreciate some of its values. There was a closeness of family, a commitment to duty, to stoic responsibility, which I think we have to say weren’t entirely bad.”

Albert Ramsdell Gurney Jr. was born Nov. 1, 1930, in Buffalo. His father owned a real estate and insurance business.

Mr. Gurney, who was known as Pete throughout his life, wrote his first play in kindergarten and made it clear that he had no interest in joining his father’s business. He attended the private St. Paul’s School in Concord, N.H., and graduated from Williams College in Williamstown, Mass., in 1952. (He was two years behind another major figure of the stage, Stephen Sondheim.)

After serving in the Navy, Mr. Gurney went to the Yale School of Drama, receiving a master’s degree in 1958. He taught at a private school before joining the faculty of the Massachusetts Institute of Technology, where he taught literature, drama and the humanities for more than 25 years.

In the meantime, he wrote plays in the summers and had little success at first. He had a minor breakthrough in 1971 with “Scenes From American Life.”

He did not write “The Cocktail Hour” until after his father’s death in 1977.

“He didn’t like at all what I wrote,” Mr. Gurney said in 2007. “He felt I was betraying, revealing things I shouldn’t reveal, embarrassing the family and using language which he thought was vulgar and unattractive.”

Survivors include his wife of 60 years, the former Molly Goodyear of New York and Roxbury, Conn.; four children; a brother; a sister; and eight grandchildren.

Mr. Gurney also published three novels and continued writing plays until the end.

“He handed in a play last week,” his agent, Lomma, said in an interview. “Its title is ‘Final Follies.’ ”

Although seemingly about a small stratum of U.S. society, Mr. Gurney’s plays have proved popular around the world, in cultures far removed from the old Eastern elite.

“I’ve been occasionally nailed by the critics for limiting my sights to a small entity,” Mr. Gurney told the Los Angeles Times in 1998, “but I’ve always believed that if you’re accurate and true to what you’re writing about, the play will have a larger human dimension. People are people.”