Quinoa and oats are both healthy complex carbohydrate sources, but there are slight nutritional differences between them. While quinoa is technically a seed, it's consumed as a grain like oats. Both quinoa and oats have a nutritional composition that makes them effective in building muscle, thanks to their mix of carbohydrates, protein and micronutrients.

Filling Glycogen Stores With Carbohydrates

Sufficient energy intake in the form of carbohydrates is required to build and maintain glycogen, or stored energy, which is important for building strength and muscle. A study published in April 2003 in the “Journal of Applied Physiology” found that the ingestion of 100 grams of carbohydrates after resistance exercise increased net muscle protein balance, a measurement of muscle growth vs. muscle breakdown. According to the U.S. Department of Agriculture's National Nutrient Database, 1 cup of cooked quinoa contains 39.4 grams of carbohydrates, while 1 cup of cooked oats contains 28 grams of carbohydrates.

Repairing Muscle Tissue With Protein

Protein is a major nutrient essential for building muscles, and to maximize their strength and muscle gains, bodybuilders generally have a maximum intake requirement of 1.7 grams of protein per kilogram of body weight per day, or about 0.75 gram per pound of body weight. According to a study published in March 2008 in the “European Journal of Sport Science,” consumption of at least 10 grams of protein with carbohydrates post-exercise is effective to increase muscle growth and stored energy. According to the USDA National Nutrient Database, 1 cup of cooked quinoa contains 8 grams of protein, while 1 cup of cooked oats contains 6 grams of protein.

Complete and Incomplete Protein

Quinoa is one of the only plant sources that offers complete protein content -- proteins that contain every type of amino acid needed by the body in sufficient amounts. Most complete protein sources come from meats and animal products, making such protein sources potentially high in saturated fats and incompatible choices for vegetarians and vegans. Animal proteins are used more readily and efficiently in the body than incomplete plant sources, but complete proteins from plants are used just as efficiently, making the protein in quinoa slightly easier for the body to use than protein in oats.

Building Muscle With Vitamins and Minerals

Several vitamins and minerals are also necessary to work out and build muscle effectively. For example, the body requires B vitamins to convert carbohydrates into energy and utilize protein properly. The mineral iron is responsible for transporting oxygen in the bloodstream and in muscles. A 1-cup serving of cooked quinoa contains 2.76 milligrams of iron and 0.76 milligram of vitamin B-3, while a 1 cup serving of cooked oats contains 2.11 milligrams of iron and 0.5 milligram of vitamin B-3, though fortified oats are available with higher micronutrient content.

The Best Choice

Quinoa and oats are highly similar in nutritional composition, but quinoa is higher in protein and offers complete protein compared to oats’ incomplete protein. If given the option, choose a fortified grain over its unfortified counterpart. Fortified grains contain more micronutrients and stand as better choices upon comparison to other varieties.