Cook the couscous. Place couscous in a heatproof bowl.
Pour in boiling water or broth, cover, and let sit for 5 minutes. Uncover and fluff with a fork to separate the grains. Let it cool to room temperature.
Make the dressing. In a small bowl or jar, whisk together olive oil, lemon juice, lemon zest, garlic, Dijon, oregano, salt, and pepper until slightly thick and well combined.
Taste and adjust lemon or salt as needed.
Prep the veggies. Halve the tomatoes, dice the cucumber, finely chop the red onion, slice the olives, and chop the roasted red pepper, parsley, and mint.
Combine. In a large bowl, add the cooled, fluffed couscous. Fold in tomatoes, cucumber, onion, olives, roasted red pepper, parsley, and mint.
Add feta and dress. Sprinkle in the feta. Pour over most of the dressing and toss gently to coat, adding the rest if needed.
You want the salad glistening, not soggy.
Rest and serve. Let the salad sit for 10–15 minutes so the flavors meld. Taste again and adjust salt, pepper, or lemon. Serve at room temperature or chilled.