If desired, heat taco shells as directed on package.
Heat oil in large nonstick skillet over high heat until hot. Add eggplant, bell pepper, onion and garlic; cook and stir 3 to 5 minutes or until vegetables begin to brown. Cover; remove from heat. Let stand 5 minutes to soften vegetables. Stir in taco sauce, salt and pepper.
To serve, spoon about 2 tablespoons vegetable mixture into each taco shell. Top each with sour cream and, if desired, additional taco sauce.