For the Chermoula: Combine the onion, garlic, cilantro parsley, and mint in a food processor and blend to a paste. Stir in the paprika, pepper, salt, coriander, and cayenne. Whisk in the lemon juice and oil until blended. Pour the chermoula over the mushrooms, cover, and set aside for 30 minutes.
On long skewers, thread 4 mushrooms and 4 pepper pieces alternatively for each serving. Cover and refrigerate.
For each serving: Lightly drizzle a skewer with oil and grill over high heat for about 2 minutes. Turn the skewer carefully with tongs and grill for about 3 more minutes. Serve immediately.
Note: The skewers can be served over rice or with a fresh green salad.