How is Their Eyes Were Watching God feminist?
In addition to the instances mentioned in the other answer, Their Eyes Were Watching God reveals itself as a feminist novel via the frame story that bookends the novel. At the very beginning, Janie is returning to her old home in Eatonville, where she lived with her second husband Joe Starks. Upon appearing on the road, in dirty overalls, the locals begin to talk about her. She pays them very little mind and continues past. Shortly after, her friend Pheoby leaves the gossips behind on the porch and goes to Janie's house. After a few minutes of talking, Janie brings up the gossips, saying, "Well, Ah see Mouth-Almighty is still sittin' in de same place. And Ah reckon they got me up in they mouth now" (5). When Pheoby acknowledges that the gossips where talking about Janie, Janie adds, "If God don't think no mo' 'bout 'em then Ah do, they's a lost ball in de high grass" (5). Here Janie shows that she doesn't care about the opinions of anyone else in town. She has returned from her long journey stronger than when she left. During her time with Tea Cake, she learned the value of her own hard work, and she came to understand her own self-worth when she was forced to make the tragic decision to kill him to save her own life.
When Hurston returns to the frame at the very end of the novel, Janie further clarifies her own strength and self-reliance as she expands on her view of the gossips, saying
Now, Pheoby, don't feel too mean wid de rest of 'em 'cause dey's parched up from not knowin' things. Dem meatskins is got tuh rattle tuh make out they's alive. Let 'em consolate theyselves wid talk. 'Course, talkin' don't amount tuh uh hill uh beans when yuh can't do nothin' else. And listenin' tuh dat kind uh talk is jus' lak openin' yo' mouth and lettin' de moon shine down yo' throat. It's uh known fact, Pheoby, you got tuhgo there tuh know there. Yo' papa and yo' mama and nobody else can't tell yuh and show yuh. Two things everybody's got tuh do fuh theyselves. They got tuh go tuh God, and they got tuh find out about livin' fuh theyselves."
Again, Janie shows just how far she has come in life. She started out mostly helpless, betrothed to one man and then another man, but her time with Tea Cake helped her to fully realize her own capabilities and live for herself. She has returned home not only a completely independent woman, but a completely independent black woman. This makes Their Eyes Were Watching God not only a feminist novel, but an intersectional feminist novel, thus showing that Hurston's novel is far more progressive than many understand.
This novel features the first strong, independent black woman in a novel to search for her identity and happiness. In those respects, Janie is a very forward-thinking, powerful female protagonist, something relatively advanced for the time period in which the book was published. Although she is a victim again and again of male repression/domination, Janie stands up for herself at several points throughout the novel.
For example, after essentially being forced into marriage with Logan Killicks, Janie leaves him when Jody Starks comes along. This would be practically unheard of in the 1930's: a woman simply picking up and leaving her husband behind. But Janie is searching for her true self, and for her life partner, and she's not going to let any man stop her. However, she soon finds herself in a very similar situation with Jody. One might expect her to up and leave, just as she did with Logan. But you need to take cultural context into consideration: she is a woman, a black woman, who has no rights to speak of in this society. She imagined that her life with Joe would be free and easy, & to some extent it is. That is the financial aspect of the relationship. Joe is a successful man, and Janie reaps the material benefits of that success. But I think that as soon as Janie realizes what her life has become, & how much Joe hurts her/oppresses her, she stands up for herself. She tells him off, in a way that is purposely emasculating (making fun of his genitalia) in front of the other men, no less. After that, she doesn't let Joe tell her what to do or control her in any way. In fact, the power in the relationship shifts from him to her, and she proves herself a strong woman of the times.
She finds her equal in Tea-Cake, although some argue that this novel cannot be feminist, in that Tea-Cake hits her and controls her in much of the same way as her first two husbands. However, there is a difference there; Janie respects Tea-Cake as an equal, and he treats her as one (for the most part). Not to make excuses for the abuse, but there's a different tone in their time together as opposed to the first two journeys of Janie's life.
It's important not to judge Janie according to our contemporary standards of feminism. We must understand that any attempt to lead an independent life was a strong statement for women in the 1930's.