Boil the dry orzo in a large pot of heavily salted water for 8 to 9 minutes until it reaches an al dente texture.
Drain the pasta in a fine mesh strainer and rinse it thoroughly under cold running water until completely chilled.
Whisk 3 tablespoons of the reserved sun-dried tomato oil, lemon juice, grated garlic, salt, and pepper in the bottom of a large bowl.
Toss the cold, rinsed orzo in the dressing until the grains are fully coated and glossy.
Fold in the chopped sun-dried tomatoes, toasted pine nuts, arugula, and crumbled feta cheese right before serving.