01 - Preheat your grill to medium-high heat, approximately 375-400°F, ensuring even cooking across the grates.
02 - Toss sliced bell peppers and onions with olive oil in a large bowl. Season generously with salt and black pepper, tossing to coat evenly.
03 - Whisk together Dijon mustard, honey, apple cider vinegar, and BBQ sauce in a small bowl until smooth and fully incorporated.
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 to an internal temperature of 160°F.
05 - Add seasoned peppers and onions to the grill using a grill basket or foil tray. Cook for 8-10 minutes, stirring occasionally until tender and slightly charred.
06 - During the final 2 minutes of grilling, brush sausages generously with the mustard glaze, turning to coat all sides evenly and allowing the glaze to caramelize slightly.
07 - Transfer sausages to a serving platter and top with grilled peppers and onions. Drizzle any remaining mustard glaze over the top before serving.