Prepare the quinoa according to package instructions. You can use a microwave packet for convenience if you wish!
While quinoa is cooking, dice cucumber, bell pepper, red onion, and spinach. Crumble feta cheese if not already done. Finely slice your avocado.
Once quinoa is finished cooking, let cool for 15-20 minutes.
Assemble all ingredients. Toss until thoroughly combined.
For the lemon vinaigrette:
In a small bowl or jar, whisk together lemon juice, lemon zest, olive oil, mustard, and seasonings.
Chop fresh sage leaves into small pieces and whisk with other ingredients.
Using an immersion blender, blend the dressing together until thoroughly mixed.
Notes
Store in an airtight container separate form the dressing for up to 3 days. I also suggest leaving out the avocado until just before enjoying to avoid browning.