Add the red pepper and cook until blistered, stirring occasionally for 4 to 5 minutes. Remove and set aside.
Add the sausage to the skillet and cook until browned, remove and set aside.
Add more olive oil if necessary and add onions, garlic, and a pinch of salt and pepper, cooking on medium high for 30 seconds to a minute. Reduce heat to medium-low and cook for 2 to 3 more minutes, until the onions are soft and translucent.
Add the mushrooms and cook 3 to 4 minutes until they are soft and have released all their juices.
Add the red peppers and sausage back into the skillet, stir.
Turn off the heat and add the squash and zucchini noodles. Stir until well mixed and the veggie noodles are slightly cooked and tender.