In food-storage plastic container or resealable food-storage plastic bag, mix marinade ingredients. Add olives and bell pepper squares; cover container or seal bag. Turn to coat well with marinade. Refrigerate 2 hours or overnight, occasionally turning container or bag to coat with marinade.
To serve, remove olives and pepper squares from marinade; discard marinade. Arrange tomatoes, cut side down, on serving plate. Thread 1 olive and 1 pepper square onto each cocktail pick. Insert each into tomato half for base.