Combine first 5 ingredients in a small bowl; stir in 1/4 teaspoon salt and 1/8 teaspoon pepper. Set aside.
Heat a large nonstick skillet over medium-high heat. Coat the pan with cooking spray. Sprinkle both sides of steak with remaining 1/4 teaspoon salt and remaining 1/8 teaspoon pepper; add steak to pan. Cook 5 minutes on each side or until desired degree of doneness. Remove from pan; let stand 5 minutes. Cut into 1/4-inch-thick slices. Keep warm.
Wipe pan with a paper towel; return to heat. Recoat pan with cooking spray. Add the potatoes; sauté 15 minutes or until browned and thoroughly heated, stirring occasionally. Serve with steak and sauce.