In food storage plastic container or resealable plastic bag, combine all marinade ingredients; mix well. Add olives and yellow pepper squares; cover container or seal bag. Turn to coat well with marinade. Refrigerate 2 to 4 days, 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 toothpick. Insert each into tomato half for base.