Get your oven ready by preheating it to 400°F (200°C).
In a skillet, heat oil over medium-high heat. Cook the celery, bell peppers, and onion for two minutes.
As you wait, get the mushrooms ready by washing them, removing the stems, and chopping half of the stems.
Once the mushroom stems are chopped, include them in the skillet with the onion and celery mixture and cook for an additional 2 minutes.
In a bowl, combine crab claw meat, crushed crackers, half of the cheddar cheese, garlic powder, old bay seasoning, egg, and salt and pepper.
Mix all the ingredients until they are well incorporated.
Position the mushrooms in a baking dish.
Spread the prepared mixture evenly into the mushroom caps and sprinkle the remaining cheese on top.
Place the stuffed mushrooms in the oven and bake for 15 minutes.
The final step is to enjoy your mouthwatering stuffed mushrooms while still warm.