Cook the pasta according to package directions and drain (see note).
Meanwhile, in a medium bowl whisk the yogurt, Italian dressing, Ranch powder, and agave until smooth.
Chop the vegetables into bite size pieces.
Toss the pasta, veggies, and feta together in a serving bowl. Drizzle half of the dressing on top, tossing to coat. Add more dressing, based on preferences (I use it all).
This is best after it's sat for at least an hour, but you can serve immediately. Keeps well in the fridge for several days.
Notes
Nutritional estimate is based on using whole wheat pasta and all of the dressing. Makes approximately 16 1-cup servings. Makes 8 reasonable sized servings as a main dish (~2c). The serving size varies based on the size of your veggies + your type of pasta. Gluten free pasta does not always plump as much, so the serving size may be slightly smaller -- I recommend adding extra broccoli or peppers to bulk it up. If you prefer your veggies a little less raw, put the chopped broccoli and peppers in a colander. When you drain the pasta, pour the hot water and pasta directly over the vegetables. Let the hot noodles sit on top of the veggies for a few minutes and you'll away a little of the raw crunch from the veggies.