NEW YORK — Marion Cunningham, a former California homemaker who overcame agoraphobia later in life to become one of America’s most famous and enthusiastic advocates of home cooking, died Wednesday in Walnut Creek, Calif. She was 90 and had Alzheimer’s disease.

John Carroll, a family friend, confirmed the death.

‘‘More than anyone else, she gave legitimacy to home cooking,’’ said Michael Bauer, the executive food editor of the San Francisco Chronicle. ‘‘She took what many people would say was housewife food and really gave it respect by force of her own personality.’’

Mrs. Cunningham’s most enduring trait may have been her ability to make even novice cooks feel as if they could accomplish something in the kitchen. She took many of them under her wing and drew from them for her popular book ‘‘Learning to Cook.’’

She loved to go to the supermarket and peer into the baskets of startled strangers, whom she would then interview about their cooking skills. She made it her life’s work to champion home cooking and preserve the family supper table.

It was a theme she focused on in the preface to ‘‘The Fannie Farmer Cookbook,’’ the classic American volume that she was hired to revise in the late 1970s.

‘‘Too many families seldom sit down together; it’s gobble and go,’’ she wrote, ‘‘eating food on the run, reheating it in relays in the microwave as one dashes off to a committee meeting, another to basketball practice. As a result we are losing an important value. Food is more than fodder. It is an act of giving and receiving because the experience at table is a communal sharing; talk begins to flow, feelings are expressed, and a sense of well-being takes over.’’

Marion Enwright was born in Los Angeles. She grew up as a Southern California beach girl, in her words, and graduated from high school in Los Angeles.

In 1942 she married Robert Cunningham, a medical malpractice lawyer, and moved to San Diego, where he was serving in the Marines. At a time when men were in short supply for many civilian jobs, she worked in a gas station. They eventually settled in Walnut Creek, outside Oakland.

Mrs. Cunningham spent the first half of her adult life mostly raising her children, Mark and Catherine — who survive her — and tending to the family’s ranch home in Walnut Creek. And for much of that time she struggled with agoraphobia, a fear of open and public places. It was so intense at times that she could barely cross the Bay Bridge to San Francisco.

She also developed a drinking problem, and once she stopped, she became known for her love of a good cup of black coffee — sometimes ordered when everyone else was drinking champagne.

Prompted by a friend’s invitation in 1972 to go to Oregon to attend cooking classes led by renowned food writer James Beard, Mrs. Cunningham overcame her phobia and headed out of the state for the first time.

Beard took to this tall, blue-eyed homemaker, and for the next 11 years she was his assistant, helping him establish cooking classes in the Bay Area. The job gave her a ringside seat to a period in American cooking when regional food, organic produce, and a new way of cooking and eating were just becoming part of the culinary dialogue.

Her association with Beard also gave her the big break of her career, in the late 1970s, when he passed her name to Judith Jones, a well-known New York culinary editor, who was looking for someone to rewrite ‘‘The Fannie Farmer Cookbook.’’

That project led to seven more cookbooks; her own television show, ‘‘Cunningham & Company,’’ which ran for more than 70 episodes, sometimes on the Food Network; and a longstanding cooking column for the Chronicle.

In 1989 she and a friend started the Baker’s Dozen, an informal group of San Francisco bakers. It grew to more than 200 members and led to another cookbook.

Mrs. Cunningham bought a Jaguar with her first royalty check from ‘‘The Breakfast Book,’’ one of her most enduring cookbooks. The Jaguar became identified with her, and she drove it to a different Bay Area restaurant almost every night, sometimes logging 2,500 miles a month.

Along the way she collected a passel of friends who changed how America cooked and ate, including her close friend Chuck Williams, whose kitchenware company, Williams-Sonoma, was just getting started.

One of the people she discovered was a young Alice Waters, who was cooking organic and local food at a little restaurant in Berkeley, Calif., called Chez Panisse. Mrs. Cunningham took Beard to the restaurant in 1974, and he put it on the culinary map, marking the beginnings of California cuisine and the modern organic movement.

‘‘She was always my biggest cheerleader,’’ Waters once said in an interview. ‘‘I just can see her even now with her coffee and coffeecake. That’s kind of where she liked to live.’’

Plain-spoken and quick with a quip or a gentle jab, Mrs. Cunningham could cut through the puffery of fancy chefs and food writers. Once, after a food author spent the day watching her make pie crust, taking meticulous notes on how many times she cut and stirred, she called Ruth Reichl, an author and a former restaurant critic for The New York Times,.

‘‘He really is crazy, dear, don’t you think?’’ Reichl recalled her saying. ‘‘Nobody could make a decent crust following those directions.’’

Her humor extended to her cookbooks. In one passage from ‘‘The Fannie Farmer Cookbook,’’ on how to crack fresh coconut, she suggested throwing it on a patio.

‘‘That’s how monkeys do it,’’ she wrote ‘‘and they are professionals.’’