Quarter the sweet peppers lengthwise; remove and discard the stems, seeds, and membranes.
Brush eggplant slices with oil. Grill eggplant slices and sweet pepper quarters on the rack of an uncovered grill directly over medium-hot coals for 4 minutes. Turn and grill 3 to 5 minutes more or until eggplant is tender and sweet peppers are slightly charred. Remove vegetables from grill; set aside.
Spread 1 side of each French bread slice with goat cheese and mustard. Layer 3 eggplant slices and 2 sweet pepper quarters on 4 of the bread slices. Top with remaining bread slices. Serve warm. Makes 4 servings.