In a 10- to 12-inch nonstick frying pan over medium-high heat, frequently stir bell pepper, onion, and garlic in oil until vegetables begin to brown, 8 to 10 minutes. Add artichokes, parsley, olives, and lemon juice, mixing well. Remove from heat. Season to taste with salt and pepper. If making up to 1 day ahead, cover and chill.
Arrange baguette slices in a single layer on a 12- by 15-inch baking sheet. Broil 4 to 6 inches from heat until toasted on 1 side, about 1 minute. Remove from oven and turn slices over.
Spoon artichoke mixture equally on untoasted side of baguette slices; spread level. Sprinkle with cheese.
Broil 4 to 6 inches from heat until cheese begins to melt and topping is hot, about 1 minute.