Cook spaghetti pasta according to package instructions until al dente. Drain and set aside.
Heat olive oil in a large skillet over medium heat. Add diced onion, green bell pepper, and minced garlic. Sauté until vegetables are soft, about 5 minutes.
Add ground beef to the skillet. Cook, breaking up the meat with a spoon, until browned and cooked through, about 7-8 minutes. Drain excess fat if necessary.
Stir in diced tomatoes, tomato sauce, chili powder, and barbecue sauce. Season with salt and black pepper to taste.
Reduce heat to low and simmer the sauce mixture for 10 minutes, allowing flavors to meld and sauce to thicken slightly.
To serve, twirl the spaghetti into a neat mound on each plate. Spoon the saucy meat and vegetable mixture over the top.
Garnish with chopped fresh parsley before serving.