Spread one side of each bread slice with equal amounts pesto sauce. Arrange in a single layer on a baking sheet, pesto side up. Layer each slice with eggplant, red bell pepper, red onion, tomatoes, mushrooms, and cheese. Crush garlic on top of cheese, and season with oregano, basil, salt, and pepper.
Broil 5 minutes in the preheated oven, or until cheese is melted and lightly browned.