The U.S. Army needs more horses for the Spanish-American War. Hoppy must turn his Bar 20 cowhands into Rough Riders to gather up the horses, and of course bad guys try to sabotage the operation.
| Actor | Role |
|---|---|
 William BoydHopalong Cassidy | Hopalong Cassidy |
 Russell HaydenLucky Jenkins | Lucky Jenkins |
 George 'Gabby' HayesWindy Halliday | Windy Halliday |
 Judith AllenBarbara Allen | Barbara Allen |
| BBilly KingBoots | Boots |
 Alexander CrossBlack Jack Carson | Black Jack Carson |
 Karl HackettMajor McCready | Major McCready |
 Bob KortmanHawks | Hawks |
 Jack RockwellShorty | Shorty |
| JJohn BeachSmokey | Smokey |
 Ray BennettBrad | Brad |
 Philo McCulloughJordan | Jordan |
 Ben CorbettFort Guard | Fort Guard |
 Jim CoreyHenchman | Henchman |
 Earle HodginsMajor Jordan | Major Jordan |
| JJohn JuddArmy Lieutenant | Army Lieutenant |
| CClyde KenneyCourier | Courier |
| LLeo J. McMahonArmy Corporal | Army Corporal |
| BBuck MorganHoppy Man | Hoppy Man |
 Cliff ParkinsonHenchman | Henchman |
| JJohn PowerFort Cook | Fort Cook |