Combine couscous and water in a small bowl; let stand for 20 to 30 minutes, or until the couscous is tender and the water is absorbed.
Meanwhile, heat oil in a small nonstick skillet over low heat. Add bell pepper, garlic, thyme, curry powder, cumin, allspice, ginger, salt, pepper, paprika and cayenne. Cook, stirring, until the bell pepper is slightly softened, 1 to 2 minutes. Let cool.
Prepare a grill or preheat the broiler.
Combine turkey, the couscous and the bell-pepper mixture in a medium-sized bowl; mix thoroughly but lightly. Shape into four 3/4-inch-thick patties. If using the grill, oil the grill rack (see Tip) or oil the broiler pan. Grill or broil the patties until browned and no longer pink inside, about 5 minutes per side. Place on buns (or English muffins) and garnish with tomato slices and lettuce leaves.
To oil a grill rack, oil a folded paper towel, hold it with tongs and rub it over the rack. (Do not use cooking spray on a hot grill.)