Toast walnuts in a skillet on the stove, tossing until you begin to smell them and they begin to turn a golden color. Remove, cool and set aside. Cook bacon until cooked through and crispy. Drain on paper towels to remove excess fat. Cool and crumble.
Toss together the spinach, onion, toasted walnuts and strawberries. Top with crumbled feta cheese and cooked and crispy crumbled bacon and croutons. Drizzle the salad dressing and toss.
Additional *optional protein, such as grilled chicken, shrimp or scallops may be added.