Heat oil in a large pot over medium heat; stir in onion. Cook and stir until the onion has softened and turned translucent, about 5 minutes.
Add potatoes, cabbage, salt, and pepper. Add water to cover and bring to a boil. Reduce heat to a simmer and cook until potatoes are tender, about 20 minutes.
Add diced tomatoes, corned beef, cream-style and kernel corns, and pepper. Cook until heated through, about 15 minutes.