Preheat oven to 400°F (200°C).
In a large 9×13-inch baking dish, combine diced onion, bell pepper, mushrooms, garlic, dried basil, dried parsley, red pepper flakes, and salt.
Drizzle with olive oil and toss until evenly coated.
Bake for 15 minutes until vegetables begin to soften.
Remove from oven and stir in chopped spinach until slightly wilted.
Add diced tomatoes and ricotta cheese, stirring until fully combined.
Stir in dry orzo and broth, ensuring everything is evenly mixed.
Return to oven uncovered and bake for 15 minutes.
Remove, stir well, then bake another 10–15 minutes until orzo is tender and most liquid is absorbed.
Sprinkle shredded mozzarella evenly over the top.
Bake an additional 5–10 minutes until cheese is melted and bubbly.
Optional: Broil for 1–2 minutes for a golden top.
Rest for 5 minutes before serving. Garnish with fresh basil.
Vegetable and Ricotta Baked Orzo is best served warm and creamy straight from the oven.