Place the walnuts in a small skillet over medium-high heat; toast the nuts while stirring constantly for 4 to 5 minutes; set aside to cool completely.
Toss together the spinach and romaine lettuce in a large mixing bowl, and toss with 1/2 cup of balsamic vinaigrette. Arrange the strawberries, pears, feta cheese, and walnuts over the top of the salad. Dress the salad with another 3 tablespoons vinaigrette to serve.