Blueberry Spinach Summer Salad

I found this in the most recent Penzeys catalog I got.  It reminds me of the spinach salad that I made for Easter...my recipe was Spring-ish and this is Summer-ish. 

1 bag spinach, stems removed, rinsed well and dried
1 small red onion, thinly sliced
1 C. walnuts, raw or toasted (I may use pecans, I like them better)
1 C. fresh ripe blueberries
1 4oz. package crumbled feta cheese
1/3 C. regular or lemon olive oil
2-3 tbsp. balsamic vinegar
1/4-1/2 tsp. kosher salt 1/2 tsp. freshly ground pepper

Divide the spinach among 4 plates.  Tope evenly with onion slices, nuts, berries and feta.  Drizzle generously with oil and vinegar, season with salt and pepper.