Prepare outdoor grill with hot coals, or heat gas grill to hot, or heat oven broiler.
Coat medium-size nonstick skillet with olive oil cooking spray. Add sausage; saute over medium heat until sausage starts to brown slightly, 3 to 4 minutes. Add onion; saute until softened, 2 to 3 minutes
Add tomatoes, ketchup, garlic salt and pepper to skillet; simmer 15 minutes or until slightly thickened but still chunky. Stir in basil.
Meanwhile, grill or broil polenta 3 to 4 minutes per side or until golden brown and heated through.
To serve, arrange 3 slices of polenta on each plate. Top with sausage mixture. Makes 4 servings.