Rinse and drain farro, then cook according to package instructions. Transfer to a large mixing or serving bowl.
While the farro cooks, prepare the dressing: In a small bowl or large measuring cup, whisk together the olive oil, red wine vinegar, Dijon, honey, oregano, salt, and pepper until evenly blended. Pour half of the dressing over the warm farro and sprinkle with 1/4 teaspoon salt. Toss to coat.
Add all of the remaining ingredients to the bowl except for the feta: sundried tomatoes, cucumber, roasted red pepper, cherry tomatoes, peas, and parsley. Toss to coat. Taste and add as much of the remaining dressing as you like. Sprinkle with feta, lightly toss again, then season with salt and pepper to taste. Serve cold or at room temperature.
*I liked to use dried packaged sundried tomatoes instead of oil packed, as I find the salad has enough oil with the dressing. If you prefer sundried tomatoes in olive oil, you can swap them here. To rehydrate (you may or may not need to do this; if the sundried tomatoes seem moist and plump, you can skip this step): Place in a small bowl and cover with boiling water. Let rest a few minutes, then drain and use as directed.
Store leftovers in the refrigerator for up to 3 days. If you won't be eating all the salad right away, I recommend reserving some of the dressing to moisten and revive the leftovers. If you do use all of it, you can also brighten the leftovers up with a squeeze of fresh lemon juice.
To make vegan: Omit the feta cheese; replace the honey in the dressing with light agave or simple syrup.
To make gluten free: Replace the farro (which is not gluten free) with a different grain such as quinoa or brown rice.
Nutritional information was calculated with three-quarters of the dressing. (I found I didn't need it all, so feel free to adjust to your liking.)