In a large heavy-duty plastic sealable bag combine lamb and 3/4 cup marinade and seal bag, pressing out excess air.
Marinate lamb, chilled, 1 day.
Cut bell peppers into thirty-two 2- by 1 1/2-inch pieces and blanch in a large saucepan of boiling water 30 seconds.
Drain peppers in a colander and, while still hot, in a bowl stir together with 1/4 cup marinade.
Marinate peppers, covered and chilled, 1 day.
Prepare grill.
Soak skewers in warm water 30 minutes.
Drain lamb, discarding marinade.
In a sieve set over a bowl drain peppers and reserve marinade for basting.
Thread 4 pepper pieces and 4 lamb pieces, alternating pepper with lamb, onto each skewer.
Kebabs may be assembled 1 hour ahead and chilled, covered.
Grill kebabs on a lightly oiled rack set 5 to 6 inches over glowing coals, basting with reserved marinade and turning them occasionally, about 12 minutes total for medium-rare meat.
(Alternatively, broil kebabs under a preheated broiler 2 to 3 inches from heat about 4 minutes on each side.)