Jed Clampett is told by a representative of an oil company that the swamp behind his shack is full of oil. (The oil company employee has been hauled in by Jed's daughter Elly May who asks whether she can keep him.) Later, Mr. Brewster, the head of the oil company, does a deal with Jed. Jed tells Cousin Pearl that he'll receive 25 to 100 of "some new kind of dollar." Pearl, thinking Jed has been "slickered", asks what kind of dollar he's talking about. "Million dollars," Granny, Jed's mother-in-law, replies. "Jed, you're a millionaire," Pearl says. "Yeah, that's what ...
The Clampetts begin to settle in their new home in Beverly Hills, California. They are having to adjust to things such as refrigerators (Granny remarks how a ham will require two days to thaw out), ovens and the "cement pond." Jed also is having to confront how his daughter Elly May is maturing. He tells her that he, in effect, raised her as a boy and should not have. Jethro also encounters a flamingo that he thinks is a chicken (which causes Jed to suspect Jethro has been sneaking drinks of moonshine). Meanwhile, Miss Hathaway, executive secretary to banker Milburn ...
While Grannie boils pool water for washing (due to the "lack of a pump") and Ellie May gets a feminine make-over by Miss Hathaway, cousin Pearl is back at the cabin making eyes with the visiting oil man while he gives her a ride to the nearest phone.
Mr. Drysdale panics when Mrs. Drysdale comes back from Boston early, because she'll meet the Clampetts. He sets Miss Hathaway on a plan to get them to go to Palm Springs. Meanwhile, Grannie and Jed come to think Mrs. Drysdale is a drunk and make plans to cure her.
Grannie prepares her special mash to help cure Mrs. Drysdale of her drinking problem while Jed does as Mr. Drysdale suggests and buys stock: cows, goats, pigs, and chickens! Meanwhile, Mrs. Drysdale recovers from the shock of her first meeting with the Clampetts and is convinced she's imagining things.
Grannie wants to go home because folks is so unfriendly no one has come to call. Jed convinces her they should call on them, and they find that people welcome them and give them all manner of gifts when they show up on Halloween in their normal hillbilly clothes. Also, Jed works on getting Pearl to come visit while she's trying to get hitched to the oilman and find a young man for Jethrine.
Ellie May starts wearing dresses but takes it as an insult when someone says she looks like a city girl. Mr. Drysdale talks Jed into taking in his butler and upstairs girl in a plan to civilize the Clampetts, but they don't quite understand the idea of servants. Miss Hathaway takes Jethro bowling and begins to show an interest in him.
Jed enrolls Jethro at an exclusive Beverly Hills elementary school. Millicent Schuyler-Potts, the proprietor of the school, is aghast when Jed and Jethro show up, convinced this is part of some ghastly hoax. After Jed says that banker Milburn Drysdale is his neighbor, she calls the banker. It turns out that Drysdale's bank holds the mortgage on the school. Schulyer-Potts suddenly warms to the charms of the Clampetts, even if it means accepting Jethro as a fifth grader.
When Sonny Drysdale promises to give Elly May a ring, Granny thinks he's going to propose and becomes a matchmaker. Cousin Pearl can't stand the idea that Elly May would bet married before Jethrine, so she sets to matchmaking Jethrine with Jasper Depew.
Since Mr. Brewster doesn't want to get married, but since the whole county knows that Cousin Pearl had her hat set for him, Jed comes up with a plan for her to save face by having Mr. Brewster proposed in public and then have her turn him down. Jed didn't count on Mr. Brewster's background in the theater and him making a huge production out of it.
The Clampetts pack up to return to Beverly Hills, so Jethrine tries to pack Jazzbo Depew. Elly says goodbye to her animals. Back in Beverly Hills, Miss Hathaway dresses the vamp to meet Jethro at the airport, and once home the feuding starts between Grannie and Pearl over who's running Grannie's kitchen.
Mrs Drysdale leaves for a health farm saying Mr. Drysdale is "going to have a new wife," while Mr. Drysdale tells Cousin Pearl he'd like her to keep his house. However, the Clampett's think he's wanting to marry Pearl, so Jed comes up with a plan to "save" the Drysdale's marriage.
Grannie sets Elly May's dogs and the police on Cousin Pearl to stop her yodeling, making everyone mad at her. She becomes contrite when she thinks she'll get kicked out of the clan for it, until the police find her still and she thinks Pearl turned her in.
Granny can't stand Pearl's yodeling so she reports her to the police. When one of the officers takes Pearl out, Granny thinks she got Pearl in trouble and become sad and contrite. Meanwhile, the police find her still, and new trouble results.
Mrs. Drysdale wants to get rid of the Clampett's before the arrival of Mrs. Smith-Standish, the head of a 'first family' historical society. But Smith-Standish goes to the Clampett's first and becomes enchanted with their antiques and way of life. She ropes Mrs. Drysdale's into helping with chores done the old way, to her horror.
Mrs. Drysdale continues to be forced into doing "practices from the past" by Mrs. Smith-Standish, who discovers that Jed's family is possibly the first to come the country. If so they'd be famous worldwide, but does Jed want that?
Mlle. Denise comes back for the birth of her dog's puppies, and to see Jed. They do some "courtin' and sparkin'" Mrs. Drysdale isn't nearly so happy when she finds the puppies share more in common with Duke the bloodhound than Claude the poodle.
Jed arranges a party to get Grannie out of her doldrums and invites the Drysdale. But when Mr. Drysdale's boss comes and wants to meet them for dinner, he wonders if he's going to be sent to an Alaskan bank when his boss finds out he's been lying about Jed and his family being sophisticated.
Jethro needs a health certificate to graduate from the fifth grade, so he goes to the only doctor the Clampetts know about - Mrs. Drysdale's psychiatrist. He gets nowhere with Jethro, so Pearl comes and she thinks he is testing her virtue when he tries to lay her on his couch.
Jethro finally gets his bill of health from Dr. Twombly so he can graduate the fifth grade, but Twombly really wants to talk to Grannie again. Drysdale brings him to the Clampetts' just as Grannie showed Pearl how to use a love potion, so everyone thinks Twombly's interest in Grannie is love.
When Miss Hathaway gets sick and Mr. Drysdale has to speak at a conference, Jed decides helps out by running the bank and having Elly be his secretary, while Jethro finds a speech that Drysdale accidentally uses instead of his own. All the while a new teller sucks-up to the men and flirts with the women.