Cut the red bell pepper into bite-sized pieces. Trim the asparagus, peel the lower half with a peeler, and cut into four equal lengths. Slice the king oyster mushroom into quarters lengthwise.

Heat olive oil in a frying pan over low heat. Arrange the vegetables, including pumpkin slices, in the pan. Cook for 2-3 minutes until browned, then flip and cover with a lid to steam for 1 minute. Remove the lid and cook until the vegetables are tender and browned.