In a large frying pan over a medium heat, saute olive oil and garlic. Let the garlic saute for 2 minutes, stir in the green and yellow bell peppers. Let the peppers saute for 2 minutes, stir in the onions. After two minutes add the mushrooms and green onions to the frying pan. Season the vegetables with lemon pepper to taste and stir well. Cover the frying pan and cook until all of the vegetables are tender.