Bring a medium pot of water to boil. Add some salt and olive oil. Add the dry orzo pasta and cook until al dente according to package. Once done, drain, cool by rinsing pasta under cold water, toss with a small amount of olive oil to keep the pasta from sticking together, and set aside.
In a large non-stick pan, heat 2 tbsp olive oil on medium heat. Add the minced garlic and saute until fragrant.
Immediately add the diced mushrooms and saute until most of the water from the mushrooms is released and evaporated and the mushrooms are tender.
Add in the diced tomatoes and chopped spinach, combine, and saute for a few more minutes until the tomatoes and spinach just start to cook in.
Turn off the heat.
Add the cooked orzo pasta and season with salt and freshly ground black pepper to taste.
Add in the crumbled feta cheese and toss once more.
Preheat the oven to 400 degrees.
Cut the six whole bell peppers in half lengthwise (i.e. through the stem). De-seed the bell pepper and remove any white parts inside keeping the stem intact to keep the stuffing from falling out.
Lightly grease two 9x13 glass tray.
Completely fill each bell pepper half with the orzo stuffing.
Arrange the 12 bell pepper halves in the greased glass tray open side up. Bake the bell pepper halves for 30-40 minutes uncovered.
Remove from the oven, garnish with some freshly ground black pepper, and serve hot!
Notes
Make-Ahead Tip - You can easily stuff the bell peppers ahead of time, store in the fridge, and bake when ready to serve.