Preheat the oven to 400°F. Line a baking sheet with parchment paper.
Cook quinoa according to package instructions, using broth instead of water. Fluff cooked quinoa with a fork and set aside.
Mix meatball ingredients in a large bowl and shape into 1 to 1.5-inch balls (makes 16 meatballs). Bake for 17-20 minutes, until cooked through and internal temperature reads 160°F. You can broil for the last 30-60 seconds if you like a little browning on the meatballs.
Meanwhile, mix thawed peas, crumbled feta, ½ the sliced red onion, oregano, lemon juice and lemon zest in a large bowl. Add quinoa, mix until just combined, and set aside at room temperature.
Mix cucumber, tomatoes, remaining red onion, olive oil, vinegar, oregano, salt and pepper in a large bowl.
Divide meatballs, quinoa and salad between four plates and serve.
