In a large skillet, cook the ground beef over medium-high heat until browned. Drain off any excess grease.
Add the chopped onion and bell pepper to the skillet and cook until softened, about 5-7 minutes.
Stir in the ketchup, brown sugar, Worcestershire sauce, salt, and pepper. Bring to a simmer and cook for at least 10 minutes, stirring occasionally, to allow the flavors to meld.
Serve the sloppy joe mixture hot on hamburger buns.
Notes
Optional: Top with cheese, pickles, or onions for extra flavor.