In a small bowl, stir together garlic, lemon zest and juice, Dijon and chopped parsley. Slowly whisk in olive oil; set aside.
Sprinkle tilapia with lemon-herb seasoning. Heat large nonstick skillet over medium-high heat. Spritz both sides of tilapia with nonstick cooking spray and place in skillet. Cook 3 to 4 minutes per side or until fish flakes easily with a fork. Remove fish from skillet to a serving platter.
In a large bowl, toss together arugula and parsley leaves; drizzle with prepared dressing and serve with tilapia and lemon wedges, if desired.