Thaw fish, if frozen. Cut into 4 serving-size portions. Rinse fish; pat dry with paper towels. Place fish fillets in a 2-quart rectangular baking dish. Set aside.
In a small bowl stir together lemon juice, melted margarine or butter, the 1/2 teaspoon marjoram or basil, and the ground red pepper. Drizzle fish with lemon juice mixture. Bake, uncovered, in a 450 degree F oven until fish flakes easily with a fork (allow 4 to 6 minutes per 1/2-inch thickness of fish).
Meanwhile, in a medium skillet cook onion, red or green sweet pepper, zucchini, and yellow summer squash in hot oil for 2 to 3 minutes or until just crisp-tender. Stir in parsley, garlic salt, and the 1/4 teaspoon marjoram or basil. Serve vegetables over fish. Garnish with fresh marjoram, if desired. Makes 4 servings.