Add the quinoa to a pot with 1 cup water. Bring to a boil, then reduce heat to low and cover for 15 minutes.
In a small bowl combine the olive oil, balsamic vinegar, mustard, salt, and pepper.
Cut about ¼ inch off of the top and bottom of the grapefruit so it sits flat.
Position the grapefruit with one of the flat sides down and use a sharp knife to cut in a downward motion, slicing the peel from the grapefruit.
Position the grapefruit on its side and, with a small paring knife, cut the grapefruit into sections following the natural separations. Slice these sections in half.
Chop the avocado.
In a large bowl add the cooked arugula, quinoa, dried cranberries, sunflower seeds, and avocado.