In a large skillet over medium-high heat, cook ground beef until browned. Add onion, red pepper, green pepper and garlic. Cook until vegetables are tender.
Add chili powder, cumin, paprika and season with salt and pepper. Cook for 1 minute.
Cut the tops off of the bell peppers and remove the seeds and membranes. Stuff each bell pepper with the fajita mixture.
Place stuffed peppers in a baking dish. Bake for 25 minutes or until peppers are tender.
Garnish with fresh cilantro or parsley before serving.