Cook the couscous per package instructions and set to the side in a large bowl.
While the couscous is almost done cooking, in a mixing bowl combine the olive oil, harissa seasoning, cilantro, lemon juice, salt, pepper, and crushed red pepper (optional). Stir well.
Pour the harissa seasoning mix into the couscous and stir well.
Add the diced cherry tomatoes and cucumbers. Stir well, then serve.