Preheat the oven to 400°F (200°C) °F and position the rack in the center. Lightly grease a loaf pan with oil and line a standard baking sheet with parchment paper.
Make the glaze: In a small bowl, whisk together the BBQ sauce, dark brown sugar, white vinegar, and garlic powder until well combined. Set aside.
Prepare the breadcrumbs: In a medium bowl, combine the panko breadcrumbs and milk. Set aside to soak.
Sauté the vegetables: In a skillet, heat the vegetable oil over medium heat. Add the diced onion and cook until golden and softened. Stir in the minced garlic and cook for about 30 seconds, just until fragrant. Add the diced green bell pepper and cook for an additional 1 minute. Remove the skillet from heat and let the vegetables cool slightly.
Mix the meatloaf: In a large mixing bowl, combine the ground beef, sautéed vegetables, soaked breadcrumbs, shredded white Cheddar, eggs, fresh dill, Worcestershire sauce, Dijon and yellow mustard, BBQ sauce, liquid smoke, black pepper, and salt. Mix gently until just combined. Avoid overmixing to keep the meatloaf tender.
Shape the meatloaf: Transfer the mixture to the prepared loaf pan and shape it into a loaf. Carefully invert the loaf onto the parchment-lined baking sheet.
Add the glaze and bake: Spoon half of the BBQ glaze over the top of the meatloaf and spread evenly. Bake for 40 minutes.
Finish with glaze: Remove the meatloaf from the oven, spread the remaining glaze on top, and return to the oven. Bake for an additional 20-30 minutes.
Rest and serve: Let the meatloaf rest for 10 minutes before slicing and serving.