Roast the bell peppers on a gas stove's open flame, turning them with tongs, until the skins are blackened, for about 2-3 minutes; or roast them on a rack under the broiler 2 inches from the heat, turning them every 5 minutes, for about 15 minutes. Transfer peppers to a bowl, cover with plastic wrap, and let them cool. When cool enough to handle, peel peppers starting at the stem end, carefully cut off the tops with a paring knife, and rinse out any seeds. Set aside.
Lightly coat a sauté pan with olive oil; place over medium heat. Sauté garlic until it begins to turn golden, about 1 minute. Add spinach; cook over medium heat until it wilts, about 2 minutes. Remove pan from heat. Stir in lemon juice and salt; place spinach in a bowl. Preheat oven to 350°.
In a small pot, cook couscous according to package directions (about 5 minutes). Using a spatula, add the couscous and the feta cheese to the wilted spinach, and mix well.
Line a baking sheet with aluminum foil. Generously stuff all the peppers with couscous-spinach stuffing, and place on a baking sheet. Bake on the center rack for about 8 minutes. Serve immediately.
YUM! What a great vegetarian dish! We made the whole recipe for the filling, but only used three peppers since that's what we had on hand so there's plenty filling leftover but it's so tasty I could eat the filling by itself! We used quinoa instead of couscous and let it cook in the rice cooker while we roasted the peppers on the stove. Blackening, then peeling seemed like a lot of labor so we only lightly roasted the peppers and left the skin on. Even with the slight modifications, everything turned out great! Think if we added some "mediterranean" grilled porkchops, could be a complete elegant meal.