01 - Preheat grill to medium-high heat, approximately 375-400°F.
02 - Place sliced bell peppers and onions in a bowl. Drizzle with olive oil and season generously with salt and black pepper. Toss until evenly coated.
03 - In a small mixing bowl, whisk together Dijon mustard, honey, apple cider vinegar, and BBQ sauce until smooth and well combined.
04 - Place beef sausages on the preheated grill. Cook for 10-12 minutes, turning every 3-4 minutes, until browned on all sides and cooked through with an internal temperature of 160°F.
05 - Transfer seasoned peppers and onions to a grill basket or foil tray. Place on grill and cook for 8-10 minutes, stirring occasionally, until tender and slightly charred.
06 - During the final 2 minutes of cooking, brush sausages generously with the mustard glaze, turning to coat all sides evenly. Allow glaze to caramelize slightly.
07 - Remove sausages and vegetables from grill. Serve immediately, topping sausages with grilled peppers and onions. Drizzle any remaining glaze over the top if desired.