Place the walnuts in a skillet over medium heat. Cook 5 minutes, stirring constantly, until lightly browned.

In a large bowl, toss the toasted walnuts, salad greens, oranges, and red onion.

In a large jar with a lid, mix the olive oil, vegetable oil, orange juice, sugar, vinegar, mustard, oregano, and pepper. Seal jar, and shake to mix.

Divide the salad greens mixture into individual servings. To serve, sprinkle with Gorgonzola cheese, and drizzle with the dressing mixture.