Cooking rice fully in the oven takes at least 1 hour.
To cook brown rice in the oven preheat the oven to 400 F and then take a casserole dish and place the rice, butter and salt in the casserole dish that has a cover on it.
Then pour boiling water over the brown rice in the casserole dish and stir it and place the covered casserole dish in the oven for an hour.