Big Bison was the U.S. Entry into the World Robot Expo who was stolen with the other Robots, briefly appearing at the end of Episode 1 and at the start of Episode 2 of Super Robot Red Baron.

History
When Ken came to rescue of his brother, the stolen mecha Big Bison appeared from behind a hill. Ken tried to save Kenichiro, but was forced to called for Red Baron as he became outnumbered by Iron Alliance's foot soldiers and the Mecha, but Kenichiro is executed when his collar bomb goes off. Fill with anger, Ken boarded Baron and fought Big Bison, but with the help of his SSI friends, he learned Bison's control unit was located in the back of the head. Taking the opportunity the Mecha had its back on him, Red Baron was able to dispatch it with Baron Missile.

After the Battle, Ken and the SSI mourn for Kenchiro as well the other members of the Kurenai clan, where he learned his brother spent five years preparing for the emerging of the Iron Alliance.

Arsenal: Big Bison was largely a Melee Fighter, but could fired projectiles (whether missiles or energy beam) from its mouth. It's hull was resistant to blunt impacts or energy attacks, as Red Baron couldn't make a dent and Elec-Trigger had no effect on it. It's weak point was in the back of the head where its control unit was located.

Appearance: Big Bison had a silver-colored body with a can-shaped head and two hoof-like claws on it’s hands. It has glowing yellow eyes, two revolving bison horns on each side of the head, a mouth grille, a tiny red bulb on the forehead, and a red belt-like decoration around the waist.