In a large skillet, heat oil over medium-high heat. Add onion and green pepper; cook and stir until softened, about 5 minutes.
Add ground beef; cook and stir until beef is no longer pink, about 5 minutes.
Stir in ketchup, brown sugar, Worcestershire sauce, garlic powder, chili powder, and black pepper. Reduce heat to low; simmer for 10 minutes, stirring occasionally.
Spoon beef mixture onto bottom halves of hamburger buns; top with remaining buns.
Interesting Facts
Sloppy Joes were invented in the early 20th century in the United States.
Sloppy Joes are sometimes called Manwiches.
Sloppy Joes are a popular dish at school cafeterias.