Cut sausage on an angle into 1/2” slices. Prepare quinoa according to package directions; keep warm.
Heat a large skillet over medium heat for 2 minutes; add sausage, onions and mushrooms. Cook, stirring frequently 4-5 minutes or until sausage is lightly browned and vegetables are tender. Add quinoa and spinach; cook and stir 4-5 minutes, stirring occasionally until spinach is wilted.