Slice bell peppers in half and scoop out seeds and membranes. Lay peppers, flesh side down on a foil-covered baking sheet. Place onion and garlic around peppers. Broil peppers 10 minutes or until skin is black. Move to a resealable plastic bag, seal, and let rest 15 minutes. Peel off skin.
Using a food processor or blender, puree peppers, onions, and garlic until finely diced. Blend in breadcrumbs, yogurt, vinegar, oil, salt, and hot sauce until smooth.