Place bell peppers and onion on grill rack coated with cooking spray, and grill 10 to 12 minutes or until tender. Slice bell peppers into 1/4-inchthick strips, and cut onion rings in half. Place in a medium bowl, and toss with rosemary and next 3 ingredients; set aside.
Sprinkle steaks evenly with salt and black pepper. Grill 5 minutes on each side or until desired degree of doneness. Serve vegetable mixture with steaks.