-
Heat 2 tablespoons oil in a large skillet over medium. Add onions and ½ teaspoon salt; cook, stirring occasionally, until golden brown, 12 to 15 minutes. Transfer to a bowl and let cool.
-
Meanwhile, heat 1 tablespoon oil in a large pot over medium-high. Add couscous and cook, stirring occasionally, until golden, 3 to 4 minutes. Add 2 cups water and ½ teaspoon salt. Bring to a simmer and cook, covered, until water is absorbed, 5 to 7 minutes. Fluff with a fork and spread out on a baking sheet; let cool for 15 minutes.
-
Toss onions, couscous, and corn in a bowl. (Refrigerate, covered, up to 1 day in advance.)
-
Just before serving, add basil, chives, dill, feta, pine nuts, vinegar, pepper, and remaining ⅓ cup oil and 2 teaspoons salt and toss to combine.