In a small bowl, whisk together the olive oil, lemon juice, Dijon mustard, salt, pepper, garlic powder, and chopped parsley until fully blended. Adjust seasoning to taste and set aside.

Set a medium saucepan over medium-high heat and add the olive oil. When the oil is hot, add the couscous and cook, stirring frequently, for 1 minute. Add the minced garlic and cook for an additional 30 seconds, just until fragrant. Add water and salt, then bring to a simmer. Reduce to low heat, cover, and cook without stirring for 10 minutes, until the liquid is absorbed and the couscous is al dente. Drain and rinse in cold water.

Transfer the well-drained couscous to a serving bowl. Add the prepared dressing and toss to coat evenly. Sprinkle with parsley and serve.