The season featured 9 actors credited in a starring capacity. All of the characters creditied in the third season with the exception of Chris Lowell who departed in the previous season finale when his character Dell was killed off, continue to be credited as main cast members.
Joining the principle cast are season two and three guest star Brian Benben as Sheldon. Benben was credited in a recurring capacity until the third season episode "The Hard Part" in which he was cast as 'Also Starring' in every episode in which the actor made an appearance. However, as of the season premiere, he joins the main cast on a regular basis. Caterina Scorsone, who guest starred in five third season episodes, also joins the main cast portraying Amelia.
Addison's familial crisis mid way through the season brought JoBeth Williams (Bizzy), Stephen Collins (Captain), Grant Show (Archer) and Anne Cusack (Susan) back to the series' reprising their roles as the extended Montgomery family. The season also explored the families of other characters including Pete (with One Flew Over The Cuckoo's Nest's Louise Fletcher acting as his mother), Charlotte and Cooper. The departed Dell's family was continually featured through his surviving daughter, Betsey who continued to be played by Hailey Sole.
The characters love lifes were complicated by the presence of Alex Kingston's Marla and the return of Michael Patrick Thornton as Fife. Amanda Foreman (who made a conjoining appearance as a different character in the seventh season of Grey's Anatomy) returned as Katie Kent in a catalysic appearance that would eventually lead to the disolution of the practice. The season finale featured Benjamin Bratt in a then-unnamed role which would lead to his regular appearances as Jake Reilly during the fifth season.
Episode number: 02
Original air date: September 30, 2010
Plot: In the wake of William White's death, Naomi looks for support from her co-workers in merging Oceanside Wellness and Pacific Wellcare while Addison debates going public with her new relationship with Sam after weeks of secrecy. Violet and Cooper are forced to make amendments to their friendship to please their significant others after Charlotte and Pete voice their concern while, Sheldon's decision to deny approval for Charlotte's patient's sex change backfires and Amelia continues to evade her departure for Seattle to visit her brother.
Recurring characters: None
Episode number: 03
Original air date: October 7, 2010
Plot: The Oceanside doctors are tested when the drunk driver responsible for killing Dell and endangering Maya arrives at the practice, in a bid to make amends. However, when he suffers a heart attack amidst the confrontation Sam struggles with his responsibility to help save his life, bringing back painful memories from his residency. Naomi attempts to adapt to Addison and Sam's relationship, but finds the effect on their friendship unavoidable while Charlotte begins house hunting, much to Cooper's chagrin. Pete resumes working with an old colleague for a back-door medical practice.
Recurring characters: None
Episode number: 04
Original air date: October 14, 2010
Plot: When Dell's orphaned daughter Betsey arrives at the practice, guilt and remorse surface amongst the doctors as they all consider whether or not they can take in the young girl. Violet takes temporary care of the child, in an attempt to get a second chance for her treatment of Lucas, but the strain on her family soon becomes apparent. Elsewhere, the situation forces Sam and Addison to realize their differing opinions on parenthood while Amelia comes into conflict with Pete over the treatment of a pregnant patient suffering from chronic pain.
Recurring characters:Hailey Sole as Betsey Parker
Episode number: 22
Original air date: May 19, 2011
Plot:Violet learns that her liscence to practice medicine was been revoked and the practice finds itself under attack as a consequence making the doctors questions whether to fight for Oceanside Wellness or to go their seperate ways. Meanwhile, Addison makes an effort to make a chance in her life in the wake of her break up with Sam while Charlotte faces her demons when a rape victim is admitted into St. Ambrose. Amelia's behaviour causes concern about her sobriety and Violet's decision to go on a book tour causes trouble between her and Pete.
Recurring characters:Benjamin Bratt as Jake Reilly, Michael Patrick Thornton as Gabriel Fife and Hailey Sole as Betsey Parker