Bring water to a boil in a pot. Add couscous, cover, and remove from heat. Let it sit for 5 minutes.

Fluff couscous with a fork and transfer to a mixing bowl. Add cherry tomatoes, cucumber, bell pepper, and red onion.

In a small bowl, whisk together olive oil, lemon juice, salt, and pepper. Pour over the salad and toss to combine.

Serve chilled or at room temperature.