Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add onion, and sauté 4 minutes. Add garlic, and sauté 30 seconds. Remove from heat. Combine onion mixture, breadcrumbs, and the next 8 ingredients (breadcrumbs through spinach), stirring well.
Shape meat mixture into a 12 x 5-inch loaf on a broiler pan coated with cooking spray. Brush ketchup over the top of the loaf. Bake at 350° for 45 minutes or until a thermometer registers 160°; let stand 10 minutes before slicing.