Prepare a grill for medium heat; oil grate with vegetable oil. Combine ½ cup quick-cooking couscous, 1 Tbsp. baharat, and 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt in a large heatproof bowl. Pour in ½ cup plus 2 tsp. boiling water. Cover bowl with a kitchen towel; let sit 5 minutes.

Using a fork, break up couscous (it will be a little less fluffy than usual). Add 1 large shallot, finely grated, 5 garlic cloves, finely grated, 1 lb. ground beef, preferably 20% fat, ½ cup finely chopped cilantro, ½ cup finely chopped salted toasted pistachios, 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt, and ½ tsp. freshly ground black pepper to couscous. Using your hands, gently mix to combine and set meat mixture aside.

Arrange 4 large bell peppers, halved lengthwise, ribs and seeds removed, on a rimmed baking sheet. Drizzle with 1 Tbsp. vegetable oil and season all over with salt and black pepper; turn to coat. Grill bell peppers, cut side down, until just starting to char, about 3 minutes. Return to baking sheet, arranging skin side down, and let cool.

Lightly fill each bell pepper half with about ½ cup meat mixture. Arrange, skin side down, on grate. Cover and grill until bell peppers are tender and charred underneath and filling is cooked through (an instant-read thermometer inserted into the center of filling should register at least 165°), about 20 minutes. Transfer stuffed peppers to a platter.

Meanwhile, whisk 1 cup plain whole-milk Greek yogurt or labneh, 2 tsp. finely grated lemon zest, 2 Tbsp. fresh lemon juice, and remaining ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a small bowl.

Top bell peppers with coarsely chopped salted toasted pistachios and serve with lemon yogurt on the side.