Cook the Orzo: Bring a large pot of salted water or chicken broth to a boil. Add the orzo pasta and cook according to package instructions until al dente (usually 8 to 9 minutes). Drain the pasta, reserving 1/4 cup of the starchy pasta water, and set aside.
Season the Chicken: While the pasta cooks, pat the cubed chicken breasts dry with paper towels. Toss the cubes in a small bowl with the dried oregano, garlic powder, salt, and pepper until evenly coated.
Sear the Chicken: Heat 1 tablespoon of extra virgin olive oil in a large skillet over medium-high heat. Add the chicken in a single layer. Let it sear undisturbed for 3 to 4 minutes to build a golden crust, then flip and cook for another 3 minutes until fully cooked through (internal temperature of 165°F). Transfer the chicken to a plate and set aside.
Sauté the Aromatics: Reduce the skillet heat to medium and pour in the remaining 1 tablespoon of olive oil. Add the diced red onion and bell pepper, sautéing for about 3 minutes until they start to soften.
Add the Green Vegetables: Stir the trimmed asparagus pieces, halved cherry tomatoes, and minced garlic into the skillet. Sauté for another 2 to 3 minutes until the asparagus turns vibrant green and tender-crisp, and the tomatoes just begin to blister.
Deglaze the Pan: Turn the heat down to low. Grate the lemon zest and squeeze the fresh lemon juice directly into the skillet. Use a wooden spoon to gently scrape up the flavorful, caramelized brown bits stuck to the bottom of the pan.
Combine Everything: Toss the cooked orzo and seared chicken (along with any rested juices from the plate) back into the skillet with the vegetables. Toss well over low heat for 1 to 2 minutes until everything is thoroughly warmed through. If the stir fry looks a little dry, stir in a splash of your reserved pasta water to create a light, glossy sheen.
Garnish and Serve: Remove the pan from the heat. Sprinkle the finely chopped fresh parsley over the top and serve warm.