Heat sesame oil in a large skillet over medium heat.
Add ground beef and cook until browned, breaking it apart as it cooks.
Add chopped onions and minced garlic, sauté for 2 minutes until fragrant.
Stir in diced red and green bell peppers, cooking until slightly tender.
Pour in soy sauce, black pepper, salt, and red pepper flakes, stirring well.
Add cooked rice to the skillet, mixing until well combined and heated through.
Serve hot, garnished with sliced green onions and sesame seeds.