Bring vegetable broth to a boil in a medium saucepan over medium-high heat.
Add pearl couscous, reduce heat to low, cover, and simmer for 8 to 10 minutes until liquid is absorbed.
During the last 2 minutes of cooking the couscous, add the peas to the saucepan to blanch them.
Drain any excess liquid and transfer the couscous and peas to a large mixing bowl to cool slightly.
In a blender or food processor, combine basil, olive oil, lemon juice, garlic, salt, and pepper; process until an emulsified green dressing is formed.
Add the diced red onion and crumbled feta to the bowl with the cooled couscous and peas.
Pour the basil vinaigrette over the salad ingredients and toss gently to coat evenly.
Serve immediately at room temperature or refrigerate for 30 minutes to serve chilled.