Cut peppers into 1/4-inch-wide strips and put in a wide salad bowl. Add 1 teaspoon olive oil, 3 tablespoons vinegar, garlic, and olives; mix.
Brush baguette slices lightly on 1 side with olive oil (about 1 tablespoon total). Lay oiled side up in a 10- by 15-inch pan. Bake in a 375° oven until lightly toasted, about 8 minutes; cool on a rack.
To bowl, add onion, spinach, and frisée; mix, and season to taste with more vinegar and salt.
Heat 2 tablespoons oil in a 6- to 8-inch frying pan over high heat, about 1 minute. Pour over salad and mix. Add cheese and baguette slices; mix again.