Wash roaster inside and out, and pat dry.
Zest one orange and then cut it into quarters. Slice other orange into 1/4-inch slices.
Coat cavity with 1-2 T. Olive oil and stuff with orange quarters, onion quarters, and some garlic slices. Stuff orange slices and garlic slices under loosened skin covering the breasts and thighs.
Mix remaining olive oil, orange juice, orange zest, and next 5 ingredients and set aside.
Place stuffed roaster in oven roasting bag and follow instructions on package. Also place in roasting bag any remaining orange slices or garlic slices.
Pour orange juice mixture over stuffed roaster. Tie bag and place in pan, as per instructions on package.
Bake in 350 degree oven for about 1 hour and 45 minutes or until meat thermometer inserted into thickest part of thigh reads 180 degrees . Let chicken stand 5 minutes before carving.