Prepare all ingredients by chopping onion, mincing garlic, slicing red bell pepper, and rinsing Thai basil leaves.
In a large skillet, heat vegetable oil over medium heat. Sauté garlic and onion for 3-4 minutes until translucent.
Add ground beef to the skillet, breaking it apart as it cooks. Stir occasionally until browned, about 5-7 minutes. Drain excess fat.
Stir in sliced red bell pepper, soy sauce, oyster sauce, sugar, and crushed red pepper flakes. Cook for an additional 2-3 minutes until bell pepper is tender. Fold in fresh Thai basil leaves.
Take a large lettuce leaf, spoon a portion of the beef mixture into the center, fold sides over, and roll tightly. Repeat until all filling is used.
Optional: Heat a non-stick skillet over medium heat and sear the rolls seam-side down for 1-2 minutes on each side until golden brown.
Serve with lime wedges on the side.