All 121 actors in both ER and St. Elsewhere
121 actors have appeared in both ER and St. Elsewhere, across 468 episodes. The most-credited is Bonnie Bartlett, Ruth Greene in ER and Ellen Craig in St. Elsewhere.
| Actor | In ER | In St. Elsewhere | Eps | Eps |
|---|---|---|---|---|
| Bonnie Bartlett | Ruth Greene | Ellen Craig | 2 | 36 |
| Barbara Whinnery | Mrs. Draper | Dr. Cathy Martin | 1 | 32 |
| Lily Mariye | Nurse Lily Jarvik | Nurse Sherry Long | 127 | 1 |
| Deborah May | Nursing Director Mary Cain | Terri Valere | 7 | 11 |
| Nancy Stafford | Alan's Mom | Joan Halloran | 1 | 7 |
| Byron Stewart | Mr. Layton | Warren Coolidge | 1 | 17 |
| Beah Richards | Mae Benton | Regina | 8 | 1 |
| Ernie Hudson | Colonel James Gallant | Jerry Close | 2 | 6 |
| Sam Anderson | Dr. Jack Kayson | Mr. McGrath | 19 | 1 |
| Tom Poston | Earl | Jim Morrison | 2 | 1 |
| Piper Laurie | Sarah Ross | Fran Singleton | 2 | 3 |
| Akosua Busia | Kubby Ikabo | Debra Etting | 5 | 1 |
| Karen Austin | Mrs. Carlson | Dr. Mary Woodley | 1 | 3 |
| Dan Hedaya | Herb Spivak | Joseph Keuhnelian | 4 | 3 |
| Ann Hearn | Shelly Dunleavy | Andrea Fordham | 1 | 4 |
| Jamie Rose | Marilyn Bracken | Dr. Susan Birch | 1 | 4 |
| Bill Macy | Richard Gould | Hershel Millstein | 1 | 2 |
| Ed Lauter | Fire Captain Dannaker | Stan Morgen | 6 | 1 |
| Al Ruscio | Mr. Dellanova | Raleigh, Mr. Morlin | 1 | 3 |
| Brian McNamara | Gil Brenner | Michael Endicott | 1 | 3 |
| Amanda Wyss | Mrs. Adams | Pru Dowler | 1 | 3 |
| Diane Delano | Stella Willis, Delores | Nurse | 5 | 1 |
| Ray Liotta | Charlie Metcalf | Murray | 1 | 1 |
| Scott Paulin | Dr. Kirsch | Stephen Craig | 1 | 4 |
| Roxanne Reese | Sara Dell | Nurse Louise Safford | 1 | 5 |
| Christine Healy | Administrator Harriet Spooner | Katie Ewell | 3 | 2 |
| Rita Zohar | Patient's Wife | Dr. Vera Anya | 1 | 2 |
| Jeannetta Arnette | Mrs. Hawkes | Louise Garrison | 1 | 1 |
| Christopher Allport | Mr. Strickland | Mr. Kent | 1 | 2 |
| Gina Hecht | Radiology Tech | Bonko | 2 | 1 |
| James Sutorius | Dr. Abrams | Sam Hendrix | 1 | 2 |
| Jenny O'Hara | Nurse Rhonda Sterling | Sue Follett | 2 | 1 |
| Conchata Ferrell | Mrs. Jenkins | Gina Barnett | 1 | 1 |
| Linda Kelsey | Grace Holsten | Cape Resident | 1 | 1 |
| Marilyn Child | Nun | Dr. Virginia Morgan | 1 | 2 |
| Mary-Margaret Lewis | Maid | Nurse Lynn Thornton | 1 | 4 |
| Mimi Kennedy | Sgt. O'Malley | Lois Wegener | 1 | 2 |
| Ramon Bieri | Mr. Bartok | Gene Galecki | 1 | 3 |
| Robert Costanzo | Pernicious Anemia Man | Mr. Broadwater | 1 | 2 |
| K Callan | Kelly Robinson | Patty Galecki | 1 | 2 |
| Virginia Capers | Mrs. Wilson | Admit Clerk | 2 | 1 |
| Elizabeth Ruscio | Sarah Logan | Linnia | 1 | 3 |
| John Doolittle | Mr. Desmond | TBD | 1 | 1 |
| Julie Cobb | Dr. Felicia Kind | Mrs. Moynihan | 1 | 1 |
| Louis Giambalvo | Security Guard David Hilliker | Anthony Rizzo | 1 | 1 |
| Marcelo Tubert | Galloway | Clerk | 3 | 1 |
| Sasha Mitchell | Bartender, Patrick | Southie | 4 | 1 |
| Fran Bennett | Michelle, Phyllis | Nurse Julie Attucks | 2 | 1 |
| Todd Susman | Dr. Sam Jenkins | Victor Bevine | 1 | 2 |
| Bruce Wright | George Dunleavy, Pilot Gordon | Paramedic | 2 | 2 |
| Curt Lowens | Bob Jones | TBD | 1 | 1 |
| Judyann Elder | Debra Graham | Elodie Haber | 1 | 1 |
| Julius Harris | Gramps | Earl | 1 | 1 |
| Kathleen Lloyd | Dr. Mack | Lorraine | 2 | 1 |
| Micole Mercurio | Marguerite Janeway | Mary Abernathy | 1 | 1 |
| Peggy Pope | Mrs. Gainsley | Grace | 1 | 1 |
| Juanita Jennings | ICU Doctor, Mrs. Davis | TBD | 2 | 1 |
| Charles Tyner | Barry Connelly | Christopher Seamus Payne | 1 | 1 |
| John Dennis Johnston | Mr. Hearn | Nick Moats | 1 | 1 |
| Joseph Ruskin | Mr. Kingsley | Dr. Jonas Wisner | 1 | 1 |
| Patrick Collins | Dr. Netzley | Boston Massachusetts | 1 | 1 |
| Paul Carafotes | Police Officer | TBD | 1 | 1 |
| Bruce Gray | Carter Board member, Dr. Munch | Colonel Harvey Blackwell | 2 | 1 |
| Peter Van Norden | Dr. Edwin Bain | Bill Fulkerson, Patient | 1 | 2 |
| Alex Rocco | Martin Trudeau | Roger | 1 | 1 |
| Alice Hirson | Mrs. Anderson | Anne Overland | 1 | 1 |
| Earl Houston Bullock | Thorpe | Police Sergeant | 1 | 1 |
| Eric Christmas | Mr. Heath | Jersey Piker | 1 | 1 |
| James Gallery | Seedy Man | Justice of the Peace | 1 | 1 |
| Laurie O'Brien | Mrs. Richards | Mrs. Morgen | 1 | 1 |
| Nan Martin | Mrs. Curwane | Mrs. Stevenson | 1 | 1 |
| Priscilla Pointer | Mrs. Abernathy | Marie Halloran | 1 | 1 |
| Rosalind Chao | Dr. Theresa Chow | Mary Wilson | 1 | 1 |
| Shelly Desai | Cabbie | Ahjai Sihkan | 2 | 1 |
| Viola Kates Stimpson | Ethyl, Mrs. Webb | Mrs. Konover | 2 | 1 |
| Sandy Martin | Mrs. Zarian, Sister Helen | Mrs. Lawson | 2 | 1 |
| Anne Gee Byrd | Harper | Mrs. Brennan | 1 | 1 |
| James Keane | Workman | Lawyer | 1 | 1 |
| Lou Richards | Perkins | William Craig | 1 | 1 |
| Raye Birk | Mr. Hartley | TBD | 1 | 1 |
| Steve Eastin | Lorenzo | Detective Thibideaux | 1 | 1 |
| Susan Merson | Mrs. Blum | Dr. Gail Perry | 1 | 1 |
| Wortham Krimmer | Weiss | Dave Falletta | 1 | 1 |
| Seth Isler | Kirchman | Russ Butler | 1 | 2 |
| Barbara Tarbuck | Alice Presley | Agnes Najinsky | 1 | 1 |
| Bette Ford | Princess Taffeta | Pat Kroll | 1 | 1 |
| Henry G. Sanders | Phillip | Guard Neil Baldwin | 1 | 1 |
| Ralph Seymour | tbd | Gene Castody | 1 | 1 |
| Anne Haney | Mrs. Packer | Mrs. Clifford | 1 | 1 |
| Ford Rainey | Army Armstrong | Doc Bogert | 1 | 1 |
| Wendy Phillips | Mrs. Lambright | Diane Hassett | 1 | 1 |
| Will Jeffries | Mr. Larkin | Frank Ashman | 1 | 1 |
| William Schallert | Mitchell Jennings | Dr. Olan Standley | 1 | 1 |
| Yolanda Lloyd Delgado | Elena Tabajas | Mrs. Imperi | 1 | 1 |
| Billy Gallo | Captain Hutch | Anthony | 1 | 1 |
| Eda Reiss Merin | Mrs. Heizer | Mrs. Gustas | 1 | 1 |
| Ken Magee | Security Guard Manager | Repairman | 1 | 1 |
| Patricia Gaul | Mrs. Etheridge | Mrs. Tillman | 1 | 1 |
| Holgie Forrester | Dorothy | Little Snoopy | 1 | 1 |
| Howard McGillin | Herrguth | Scott | 1 | 1 |
| Santos Morales | Mr. Zevallo | Mr. Guiterrez | 1 | 1 |
| Terrence O'Connor | Mrs. Robinson | Janet Dowler | 1 | 1 |
| David Packer | Mr. Ledbetter | Willie Andrews | 1 | 1 |
| Edith Fellows | Sadie Hubbell | Mrs. Sabin | 1 | 1 |
| Joe D'Angerio | Rezek | Janitor | 1 | 1 |
| Judy Jean Berns | Mrs. Fredriksson | Mrs. Kotlarz | 1 | 1 |
| Mari Gorman | Karlson | Policewoman | 1 | 1 |
| Matthew Faison | Dr. Weinstein | Mr. Woodman | 1 | 1 |
| Michael Fox | Mr. Bozinsky | Bradford Norton | 1 | 1 |
| Douglas Rowe | Dr. Arndt | Dr. Anspaugh | 1 | 1 |
| Duke Stroud | Uncle Liam | Willy | 1 | 1 |
| Howard George | Kuzner | Detective Enright | 1 | 1 |
| Karen Huie | Mrs. Cheung | Interpreter | 1 | 1 |
| Steven M. Gagnon | Dr. Blum | Gary Halloran | 1 | 1 |
| B.J. Ward | Romano's Post-Op Nurse | Mrs. Elway | 1 | 1 |
| Nick DeMauro | Zumbano | Jake | 1 | 1 |
| Barry Cutler | McCollum | Orderly | 1 | 1 |
| Guy Killum | Embry | Lexie | 1 | 1 |
| Bridget Sienna | Hernandez | Mrs. Rodriguez | 1 | 1 |
| Lee Ryan | Ortho #2 | Patrolman Pete Malloy | 1 | 1 |
| Pearl Shear | Mrs. Bozinsky | Mrs. Sussman | 1 | 1 |
Cast data from TVmaze, licensed CC BY-SA 4.0.