Preheat the oven to 375 degrees.
Slice peppers in half lengthwise. Trim out the white membrane and any seeds. Brush the bottom of a baking dish with ¼ cup of BBQ sauce. Place peppers cut side up on top of the BBQ sauce. Set aside.
In a large skillet, heat olive oil over medium-high and add the onions, garlic, and jalapenos (optional). Sautee until the onions are cooked through and soft, about 6 minutes. Add the ground beef and break it apart while browning.
When beef is browned and cooked through, add the cooked quinoa, the remaining ½ cup of BBQ sauce, Worcestershire, and season with salt and black pepper.
If the mixture looks a little dry, add more BBQ sauce or a little water.
Sprinkle some of the grated cheese in the empty pepper shells. Add the beef mixture and sprinkle with the remaining grated cheese. Cover the baking dish and bake for 40 minutes. Remove the baking dish and test the peppers to ensure they are soft, by poking the side wall of the pepper with a sharp knife. If peppers are still firm, return to the oven for another 10 minutes.
Serve with your favorite salad for a complete meal.