Rub outside of each portabella mushroom cap with 1 tsp. olive oil. Place on a rimmed baking sheet.
Heat 1 Tbsp. olive oil in a medium frying pan.
Add onions, mushrooms, sage, and pepper and cook over medium-high heat until onions are tender.
Add stuffing and butternut squash and cook to heat through.
Fill each portabella mushroom cap with 1 oz. cream cheese and 3/4 c. stuffing mixture.
Top each with 1 Tbsp. chopped pecans and 2 Tbsp. shredded cheese.
Bake at 350 degrees for 15-20 minutes.