01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - Toss the halved grapes with olive oil and a pinch of salt. Spread in an even layer on the prepared baking sheet. Roast for 15 to 18 minutes, until grapes are softened and caramelized. Allow to cool slightly.
03 - Combine rinsed farro, water, and salt in a medium saucepan. Bring to a gentle boil over medium-high heat. Reduce to low, cover, and simmer for 25 to 30 minutes, until tender with a chewy bite. Drain any excess water and let farro cool to room temperature.
04 - In a large mixing bowl, whisk together olive oil, white wine vinegar, orange juice, honey, Dijon mustard, salt, and black pepper until smooth and emulsified.
05 - Add cooled farro, roasted grapes, orange segments, thinly sliced shallot, and baby arugula or spinach to the bowl with the dressing. Toss gently to ensure everything is evenly coated.
06 - Fold in toasted walnuts and crumbled feta cheese, if using. Taste and adjust seasoning with additional salt or pepper as needed.
07 - Transfer to a serving platter. Serve at room temperature or slightly chilled for optimal flavor.