1. Pit and peel avocado and cut into 1/4-inch cubes. With a sharp knife, cut and discard peel and white pith from orange. Cut between membranes to release orange segments into a bowl.
2. In a strainer, rinse and drain quinoa. In a 3- to 4-quart pan over high heat, bring 1 1/2 cups water to a boil. Add quinoa and 1/2 teaspoon salt and adjust heat to maintain a simmer. Cover and cook until water is absorbed and quinoa is tender to bite, about 15 minutes.
3. Meanwhile, rinse halibut and pat dry. Sprinkle lightly all over with salt and pepper. Pour oil into a 10- to 12-inch nonstick frying pan over high heat. When hot, add halibut and cook, turning once, until opaque but still moist-looking at the center of the thickest part (cut to test), about 6 minutes total. Spread about 1 teaspoon marmalade over each piece of fish.
4. Mound quinoa on dinner plates. With a spatula, place a piece of fish on top of quinoa and arrange avocado and orange segments over fish. Sprinkle evenly with cranberries and hazelnuts.