Original Chicago cast
Steppenwolf Theatre ensemble members Rondi Reed (left) and Amy Morton in the original Chicago cast of August: Osage County.- Ian Barford* – Little Charles
- Deanna Dunagan – Violet Weston
- Kimberly Guerrero—Johnna Monevata
- Francis Guinan* – Charlie Aiken
- Rick Snyder* – Steve Heidebrecht
- Dennis Letts – Beverly Weston
- Fawn Johnstin—Jean Fordham
- Mariann Mayberry* – Karen Weston
- Amy Morton* – Barbara Fordham
- Sally Murphy* – Ivy Weston
- Jeff Perry* – Bill Fordham
- Rondi Reed* – Mattie Fae Aiken
- Troy West—Sheriff Deon Gilbeau
- Diane Dorsey—u/s Violet, Mattie Fae
- Robert E. Dennison—u/s Beverly, Charlie
- Patrice Egleston—u/s Barbara
- Lori Myers—u/s Ivy, Karen
- Peter Davis—u/s Bill (performed), Steve, Sherriff Gilbeau
- Steven Marzolf—u/s Little Charles
- Sadieh Rifai—u/s Johnna
- Zanny Laird—u/s Jean
(*) Steppenwolf Ensemble Members
Original Broadway cast
- Ian Barford* – Little Charles (succeeded during the run by Michael Milligan)
- Deanna Dunagan – Violet Weston (succeeded during the run by Estelle Parsons and later Phylicia Rashad)
- Kimberly Guerrero — Johnna Monevata (succeeded during the run by Samantha Ross)
- Francis Guinan* – Charlie Aiken (succeeded during the run by Guy Boyd and Robert Foxworth)
- Brian Kerwin – Steve Heidebrecht
- Dennis Letts – Beverly Weston (Succeeded during the run by Munson Hicks and later John Cullum and Michael McGuire)
- Madeleine Martin – Jean Fordham (succeeded during the run by Molly Ranson)
- Mariann Mayberry* – Karen Weston (succeeded during the run by Amy Warren)
- Amy Morton* – Barbara Fordham (succeeded during the run by Johanna Day)
- Sally Murphy* – Ivy Weston (succeeded during the run by Dee Pelltier)
- Jeff Perry* – Bill Fordham (succeeded during the run by Frank Wood)
- Rondi Reed* – Mattie Fae Aiken (succeeded during the run by Elizabeth Ashley)
- Troy West—Sheriff Deon Gilbeau (succeeded during the run by Scott Jaeck)
- Munson Hicks—u/s Charles, Beverly
- Susane Marley—u/s Violet, Mattie Fae
- Jay Patterson—u/s Steve, Bill, Sheriff
- Dee Pelletier—u/s Barbara, Karen, Ivy
- Molly Ranson—u/s Jean
- Aaron Serotsky—u/s Little Charles, Sherriff
- Kristina Valada-Viars—u/s Johnna
(*) Steppenwolf Ensemble Member
Original national tour cast
- Stephen Riley Key – Little Charles
- Estelle Parsons – Violet Weston
- DeLanna Studi — Johnna Monevata
- Paul Vincent O'Connor – Charlie Aiken
- Laurence Lau – Steve Heidebrecht
- Jon DeVries – Beverly Weston
- Emily Kinney —Jean Fordham
- Amy Warren – Karen Weston
- Shannon Cochran – Barbara Fordham
- Angelica Torn – Ivy Weston
- Jeff Still – Bill Fordham
- Libby George – Mattie Fae Aiken
- Marcus Nelson —Sheriff Deon Gilbeau
- Avia Bushyhead - u/s Johanna, Jean, Ivy, Karen
- Stephen D'Ambrose - u/s Beverly, Charlie
- Barbara Kingsley - u/s Violet, Mattie Fae
- Bryn Magnus - u/s Little Charles, Sherriff
- Kim Martin-Cotten u/s Barbara, Karen, Ivy
- Marcus Nelson - u/s Bill, Steve
- Cambra Overend - u/s Jean
Original London cast
- Ian Barford* – Little Charles
- Deanna Dunagan – Violet Weston
- Kimberly Guerrero — Johnna Monevata
- Paul Vincent O'Connor—Charlie Aiken
- Gary Cole* – Steve Heidebrecht
- Chelcie Ross—Beverly Weston
- Molly Ranson—Jean Fordham
- Mariann Mayberry* – Karen Weston
- Amy Morton* – Barbara Fordham
- Sally Murphy* – Ivy Weston
- Jeff Perry* – Bill Fordham
- Rondi Reed* – Mattie Fae Aiken
- Troy West—Sheriff Deon Gilbeau
- Morgan Deare—u/s Charlie, Beverly
- Anne Kavanagh—u/s Violet, Mattie Fae
- Mitchell Mullen—u/s Steve, Bill
- Lizzie Roper—u/s Karen, Ivy
- Sarah Van der Pol—u/s Jean, Johnna
- Ian Porter—u/s Little Charles, Sherriff
- Elizabeth Moynihan—u/s Barbara
(*) Steppenwolf Ensemble Member
