You can toast cooked quinoa by broiling it on high for about five minutes, tossing occasionally. Season your quinoa while cooking to make the topping even more flavorful.
Another toasting method, according to the popular quinoa manufacturer Ancient Harvest, is to whisk dry (uncooked) quinoa seeds in a sauté pan until they brown.
It's worth noting that dry quinoa is coated with a bitter substance called saponin, but you can get rid of it by soaking it in water for 10-15 minutes before cooking.