Heat olive oil in a large skillet over medium heat. Add edamame, red pepper, and garlic; cook 3 minutes, stirring frequently. Stir in 1/2 cup water, basil, chickpeas, and tomatoes; simmer 15 minutes. Add 1 3/4 cups water and salt; bring to a boil. Gradually stir in couscous. Remove from heat; cover and let stand 5 minutes. Stir in onions and feta; toss well.