Well, if you mean by "patriarchal stability" that the man is in charge of the household, then no; Mrs. Poyser continues to rule the roost in the Poyser family. In chapter 53, "The Harvest Supper," which is the last chapter in which the Poysers are part of the main action, Mr. and Mrs. Poyser are ribbing Mr. Craig about his inability to secure a wife. Of his challenges, Mrs. Poyser says,
I know what the men like—a poor soft, as 'ud simper at 'em like the picture o' the sun, whether they did right or wrong, an' say thank you for a kick, an' pretend she didna know which end she stood uppermost, till her husband told her. That's what a man wants in a wife, mostly; he wants to make sure o' one fool as 'ull tell him he's wise. But there's some men can do wi'out that—they think so much o' themselves a'ready. An' that's how it is there's old bachelors.
Mr. Poyser, who has a gentler manner than his wife, agrees that Mr. Craig should find himself a wife soon but doesn't try to give advice. Mr. Bartle jumps in,
"You pick the things for what they can excel in—for what they can excel in. You don't value your peas for their roots, or your carrots for their flowers. Now, that's the way you should choose women. Their cleverness 'll never come to much—never come to much—but they make excellent simpletons, ripe and strong-flavoured.”
“What dost say to that?” said Mr. Poyser, throwing himself back and looking merrily at his wife.
“Say!” answered Mrs. Poyser, with dangerous fire kindling in her eye. “Why, I say as some folks' tongues are like the clocks as run on strikin', not to tell you the time o' the day, but because there's summat wrong i' their own inside...”
The exchange shows that Mr. Poyser likes having a strong-willed wife who says what is on her mind. He "look[s] merrily at his wife" after Bartle's comments because he knows they will unsettle her, and he also knows the value of having an intelligent partner.
However, it's also important to note that, in spite of Mrs. Poyser's big personality, she does not resent being a wife and mother or resent her husband for being the head of the household; she relishes her role and wants to see the other young women in Hayslope find good husbands and make homes so they can be as happy as she is with Mr. Poyser. If anything stands out about a patriarchal imbalance here, it would be the relatively novel depiction of a marriage between equals in an era where there were not yet many literary examples of it.