Bring large pot of water to boil. Add orzo and cook for 8 minutes. While the pasta is cooking, make the spinach dressing by combining the spinach, olive oil, vinegars, mustard, and dried herbs in a food processor (or blender) and blending together until smooth. Set aside.
Add asparagus to the boiling pasta and cook 1 more minute. Add fresh corn and cook for 1 more minute. Drain orzo and veggies in a colander and run some cold water over it to stop the cooking. Slice corn off the cob and transfer orzo and veggies to a large bowl.
Toss with spinach dressing, red onion, tomatoes, pistachios, and feta. Salt and pepper to taste.