To prepare, coat a large nonstick skillet with cooking spray, add oil. Place over medium-high heat until hot. Add pepper strips, zucchini and onion and cook for 5 minutes, stirring often. Add 1/2 cup broth and thyme. Cover, reduce heat, and simmer 5 minutes.
Combine remaining 1/2 cup broth and flour, stirring well with a wire whisk. Add to vegetable mixture, stirring well. Cook, stirring frequently, until slightly thickened and bubbly.
Rub steaks with garlic halves; sprinkle with 1/2 teaspoon pepper. Coat grill rack with cooking spray; place on grill over medium-hot coals (350-400 degrees). Place steak on rack; grill, covered, 4 minutes on each side or to desired degree of doneness. Spoon vegetables evenly onto individual serving plates; arrange steaks over vegetables.