Harrison Beecher
Beecher's father.
- Good Parents: Has a very loving relationship with Beecher.
- No Good Deed Goes Unpunished: Taking up Keller's case to help his son gets him killed.
- Politically Incorrect Hero: From what we see of him he seems like a good man but it's implied he's a little uncomfortable with his son being queer.
- Raised by Grandparents: He takes care of Gary and Holly, Tobias' two older children.
- Small Role, Big Impact: Helping find Hank led to a lot of things happening over the course of the series.
- So Proud of You: Has this kind of moment with Beecher when he learns he wants to help a fellow inmate reunite with their estranged son.
Heinrick Schillinger
Schillinger's hateful father.
- Abusive Parents: He is horrible to Vern the few times we see them talking.
- Even Evil Has Loved Ones: He seems to have kept in touch with his daughter despite her marrying a Jewish man.
- Hate Sink: His whole reason for existing is to be a Jerkass and make Vern look good by comparison because Vern at least cares for Andrew and Hank.
- Heel Realization: On his deathbed he decides he wants to make peace with Vern.
- Jerk Ass Has A Point: He shouldn't have thrown them out but he had a right to be mad at his grandkids after they stole from him when he was letting them live under his roof.
Agent Pierce Taylor
An FBI agent investigating Keller's crimes.
- Arch-Enemy: Takes a personal interest in proving Keller's guilt for those homosexual murders and see him sent to Death Row
- Good Is Not Nice: He is not above using intimidation as a tactic to make people snitch.
- Hero Antagonist: The audience is made to root against him because Keller is one of the main protagonists, but he just wants to see Keller punished out of a genuine desire for justice for his victims.
Suzanne Fitzgerald
Ryan's real mother.
- Awful Wedded Life: Her marriage with Seamus was not a happy one and he was unfaithful to her at least once.
- Like a Son to Me: She quickly grows close to Cyril and treats him like her own.
- Morality Pet: Ryan is nothing but kind to her for the most part.
- Nice Girl: She is caring to both O'Reilly brothers and tries to help Omar as best she can.
Luis Ruiz
A member of the parole board.
- Boomerang Bigot: To a degree. He really dislikes Latinos who encourage negative stereotypes against Latinos generally, and that definitely includes Alvarez.
- Jerkass: Deliberately provokes Alvarez into attacking him in order to ruin his parole.
- Jerk Ass Has A Point: It's not hard to see why he would have a low opinion of Alvarez's character.
Hank Schillinger
Schillinger's other son, Hank is an opportunistic and somewhat sociopathic scumbag always looking for a way to make money, especially if he gets it by conning his dear old dad.
- Asshole Victim: Considering that he killed an innocent child for money it's hard to feel bad for his death.
- Boom, Headshot!: Pancamo claims this is how he was killed.
- Domestic Abuse: Pimped his wife out to several of his friends.
- Jerkass: He's a smug creep.
- Morality Pet: Vern is only ever shown to treat Hank kindly and their last scene has Vern giving him money to go on a trip, seemingly oblivious to the fact Hank is exploiting his genuine love for him to get money.
- Never Found the Body: According to Pancamo, his body is considered irretrievable.
- Would Hurt a Child: Killed Beecher's son Gary on orders from his father.
Carrie Schillinger
Schillinger's daughter-in-law and one of the few people he cares about. Unlike the rest of the Schillinger clan, she is not particularly depraved or racist.
- Broken Bird: Her husband pimped her out for money then disappeared, becoming a wanted fugitive who turns up dead, leaving her pregnant and with no friends or family she’s close to.
- Mama's Baby, Papa's Maybe: She’s unsure if her baby is Hank’s or one of her johns, although a DNA test proves the former.
- Morality Pet: To Vernon.
Eugenia Hill
Hill's mother.
- Cool Old Lady: A prim, yet caring woman whose gets along well with the other regulars visitors.
- Bearer of Bad News: She comes to tell Augustus his wife is leaving him. then dies in a bus crash on the way to tell him that.
Dean Alvah Case
A law school dean and former attorney appointed by Devlin to investigate the riot at Oz.
- Arc Hero: He serves as the main protagonist of "The Tip", but his investigation ends at the end of the episode and he serves as an offscreen presence for the rest of the series.
- The Comically Serious: It's pretty entertaining to watch the serious Case bounce off the quirky personalities that reside in Oz. Special mention goes to his brief talk with Adebisinote .(Case opens the door to Adebisi's cell)
Adebisi: (hopefully) You want to lick my balls?
(Case stares at him silently for a second and closes the door.) - Expy: He bears a lot of resemblance to Al Giardello. Both are polite, but sardonic black men who are a part of the justice system who rebel against their unethical and publicity-obsessed superiors in favor of pursuing justice.
- Gentleman Snarker: He's polite, but still very snarky.
- Greater-Scope Paragon: In Season 4, which he spends campaigning against Devlin for governor on a platform of integrity.
- Hero of Another Story: In Season 4, his campaign against Devlin is kept entirely offscreen.
- Nice Guy: Case is rather polite and has one of the firmest moral codes in the series.
- Screw the Rules, I'm Doing What's Right!: He refuses to kowtow to Devlin's demands and bribes, ultimately deciding to run against him as Governor out of spite for him.
- Screw This, I'm Outta Here: Not the investigation as a whole, which he takes seriously - but when he goes to interview Adebisi, he leaves without saying a word after Adebisi deliriously asks him to lick his balls while going through heroin withdrawal.
The Aryan Brotherhood Leader
The leader of the Aryan Brotherhood.
- Evil Old Folks: He's old enough to have a head full of white hair, and he's a real nasty piece of work.
- The Fundamentalist: Absolutely devoted to his white supremacist beliefs, and will not tolerate even the slightest degree of departure from them. "A little leaven leavens the whole loaf, that goes for you as well."
- Greater-Scope Villain: He's the real leader of the Aryan Brotherhood, or at least a high-ranking member of it, who is presumably off leading their hate crimes while Schillinger looks after the organization's interests in Oz. His only appearance has him berate Schillinger for taking him away from the much more important matters he has to attend too.
- Jerkass: He's an abrasive old bastard on top of being a white supremacist, and his entire screentime consists of insulting his followers.
Tricia Ross
Scott Ross' half-sister, she and Kareem Said fall in love but for obvious reasons they are unable to be together.
- Broken Bird
- Everyone Loves Blondes: Said certainly does.
- Harassing Phone Call: The Muslims start making these to her to get her to stay away from Said.
- Love at First Sight: Between her and Said.
- Put on a Bus: She takes her share of the lawsuit award and moves to California.
- She Cleans Up Nicely: She takes a lot more care with her appearance the second time she visits Said.
- Sibling Yin-Yang: She's basically Scott's polar opposite in every way.
- Southern Belle
- Star-Crossed Lovers: With Said.
- Thicker Than Water: She admits she and Scott were never close, didn't visit him in prison and initially doesn't want to join Said's lawsuit because she believes that Scott deserved whatever the guards did to him. At the same time she's genuinely sad that he's dead and feels guilty that she didn't come to see him while he was alive.