Zest and juice the lemon. Using a zester or grater, remove the zest from the lemon and set aside. Then, squeeze out at least 1/4 cup of lemon juice.
Make the dressing. Mince two cloves of garlic and whisk together with the lemon juice, olive oil, oregano, salt, pepper, and a pinch of lemon zest to create the dressing.
Marinate the chicken. Place chicken thighs in a bag with half of the dressing and a minced clove of garlic. Seal and massage to coat. Refrigerate for 30 minutes.
Cook the pasta. Follow package instructions to cook the pasta, then drain and allow to cool.
Cook the chicken. In a skillet over medium heat, cook the marinated chicken until browned and cooked through, about 5 minutes per side. Let rest, then chop.
Prepare the vegetables. Dice the cucumber, chop the bell pepper, halve the tomatoes, and roughly chop the parsley.
Assemble the salad. In a large bowl, combine pasta, vegetables, chicken, and crumbled feta. Add lemon zest and remaining dressing, toss to coat.