Cook pasta in salted boiling water until al dente; drain and rinse with cool water
Cool pasta completely
Chop vegetables: bell pepper, cucumber, cherry tomatoes, red onion, and/or celery
Optional add-ins: olives, artichoke hearts, chickpeas, salami, or mozzarella cubes
Make dressing: whisk olive oil, vinegar (or lemon juice), Dijon mustard, garlic, salt, pepper, and dried oregano
Combine cooled pasta, chopped vegetables, and optional add-ins in a large bowl
Add dressing gradually and toss until evenly coated
Fold in fresh herbs (parsley or basil)
Optional: add grated Parmesan and/or crumbled feta
Cover and refrigerate at least 30 minutes (up to 24 hours)
Taste and adjust seasoning before serving
Serve cold or at cool room temperature