Prepare the rice by adding the rice, oil and taco seasoning along with two cups of water to a medium pan. Bring to a boil, cover and reduce heat to low for 16-18 minutes or until rice is cooked.
Add the can of refried beans to a medium pan. Add two tablespoons of water, taco sauce and onions and stir to combine. Heat on medium until throughly heated, stirring occasionally.
Microwave the stack of tortillas on a microwave-safe plate for 30 seconds.
To assemble the burritos, layer beans, rice, sour cream, guacamole, shredded cheese, tomatoes and lettuce in each tortilla. Fold in the sides of the burrito and wrap tightly.
If you choose to grill your burrito, spray it lightly with cooking spray and heat each side in a pan on medium heat until the tortilla is golden brown. This step is optional.