Preheat oven to 425°F. Spray a large sheet pan with nonstick cooking spray or oil.

Cook rice according to package directions; set aside.

Use a spoon to remove the gills from the mushrooms and cut into ½-inch thick slices. Toss with the bell peppers, onion, olive oil, spices and salt; arrange in an even layer on the sheet pan.

Transfer pan to oven and roast for 25 to 30 minutes.

Remove pan from oven and add the black beans and cilantro to the pan, stirring to combine.

Divide the cooked brown rice between 4 meal prep containers and top each with a quarter of the mushroom fajitas.

Cover and refrigerate up to 5 days. To serve, heat to steaming and top with sliced avocado, salsa, and a lime wedge, if desired.