Pour 1 cup water, 1 tablespoon of the olive oil, and 1/2 teaspoon salt into a medium pot and bring to a boil over high heat. Add the couscous, cover, and remove from heat. Let sit until all the water has absorbed and couscous is puffed, about 5 minutes.
In a medium skillet, drizzle remaining 2 tablespoons olive oil over medium heat. Add the green onions and sundried tomatoes. Cook until heated through and beginning to soften, about 2 minutes. Stir in the garlic and cook until just fragrant, about 30 seconds.
Fluff the couscous with a fork before tossing with the vegetables. Season with the oregano, basil, onion powder, salt, and pepper. Drizzle with lemon juice right before serving.