Shrimp Brown Rice

1 Tbsp. olive oil
1 medium onion, chopped
1 medium red pepper, chopped
16 oz. sliced mushrooms
2 cups uncooked brown rice
1 tsp. minced garlic
1 tsp. saffron powder
48 oz. low-sodium chicken broth
1-2 lbs. cooked, deveined shrimp
12 oz. frozen broccoli florets
8 oz. frozen peas

In a Dutch oven, saut