Combine all cucumber-caper relish ingredients. Mix well and keep chilled until ready to use.
Boil water in a medium saucepan. Add orzo, stir, and return to a boil.
Boil orzo until al dente, 8 to 10 minutes. Drain well and set aside until ready to use.
In a large saute pan or wok, heat olive oil over high heat. Add onion, garlic, celery, and bell peppers. Stir-fry until tender-crisp, 2 to 3 minutes. Add spinach and saute until wilted, 2 to 3 minutes.
Add tomato, olives, broth, vinegar, salt, black pepper, and oregano. Bring mixture to a boil and then reduce heat to a simmer for 3 minutes.
To serve, place ½ cup of orzo on a dish, top with ¾ cup of the vegetable mixture and 2 tablespoons of cucumber relish.