If you have not already, cook the lentils and rice according to package directions, and make the marinara sauce.
Preheat your oven to 350 degrees F.
In a large skillet, heat 2 teaspoons of olive oil over medium heat.
Add the onions and garlic, and saute until translucent.
Add the mushrooms to the pan, and continue cooking until the mushrooms release their liquid, and most of the liquid evaporates.
Add the liquid smoke, lentils, rice and 1 cup marinara sauce, and warm through.
Prepare the peppers: Cut the tops off the peppers, and scoop out the insides. Arrange the peppers in a 9x13 (or similarly sized) baking dish. Spray a bit of oil in the bottom if you are worried about them sticking. If the peppers won’t sit upright, cut a small slice off the bottom until they won’t fall over.
Scoop the filling into the prepared peppers, dividing evenly. Pour a spoonful of marinara sauce onto each pepper.
Cover with a lid or aluminum foil, and bake for 30 minutes.
After 30 minutes, uncover, and bake another 15-20 minutes, until bubbly.