Trim base from fennel bulb; cut bulb into thin strips, reserving fronds for garnish, if desired.
Whisk together olive oil and next 6 ingredients in a large bowl. Add fennel strips, bell pepper, olives, and green onions, tossing to coat. Add couscous, and toss lightly.
Arrange lettuce on 6 plates. Top with couscous mixture. Sprinkle with goat cheese, and garnish with fennel fronds, if desired.