Cook meat, onion, and green bell pepper in a large nonstick skillet over medium-high heat until meat is browned, stirring until it crumbles. Drain, if necessary.
Add ketchup and next 7 ingredients; stir well. Cook, uncovered, over medium heat 10 minutes or until thoroughly heated and slightly thickened, stirring frequently.
Spoon meat mixture evenly over bottom halves of buns. Top with remaining bun halves.