The pile of raw fresh chard may look daunting, but don't worry. It cooks down to about two cups. As a meatless main course, the casserole will serve six.
2 tablespoons olive oil
2 bunches Swiss chard, washed, center ribs cut away, coarsely chopped 3 red bell peppers, chopped
1 large onion, chopped
2 cups packed grated Monterey Jack cheese (about 8 ounces)
1/2 cup grated Parmesan cheese
2 large tomatoes, thinly sliced
Grease 13x9x2-inch glass baking dish. Heat 1 tablespoon oil in heavy large Dutch oven over high heat. Add chard and sauté until wilted, about 3 minutes. Transfer chard to colander and drain well, pressing on chard with back of spoon to release liquid.
Heat remaining 1 tablespoon oil in heavy large saucepan over medium heat. Add bell peppers and onion and sauté until tender, about 8 minutes. Mix in chard and toss to combine. Mix in half of each cheese. Season to taste with salt and pepper. Spoon into prepared dish. Overlap tomato slices atop vegetable mixture, covering completely. Season tomatoes with salt and pepper. Sprinkle remaining cheeses over. Cover with foil.
Preheat oven to 350°F. Bake casserole until heated through, about 40 minutes. Uncover; bake until top begins to brown, about 10 minutes more.