In small bowl combine garlic, parsley, thyme, ¼ teaspoon salt and pepper. Rub pork with herb and garlic mixture.
Cook on preheated grill until center of pork reaches 140°, about 15 minutes. Transfer to cutting board and let rest for 10 minutes.
While pork is cooking prepare couscous. Heat 1 tablespoon oil in a medium saucepan over medium-high heat. Add the couscous and cook, stirring until toasted, about 5 minutes. Add water, ½ teaspoon salt and a few grinds of pepper.
Bring to a simmer, reduce heat to low; cover and cook until the liquid is absorbed, about 15 minutes.
Fluff couscous with a fork; let cool.
Add the feta, cucumbers, parsley, tomatoes, lemon juice and remaining 1 tablespoon of oil; toss.
Season with additional salt and pepper if desired. Serve with pork.