Add 1/3–1/2 cup instant or rolled oats to a microwave-safe bowl. Pour in 1/2–3/4 cup water, milk, or non-dairy milk. Stir to combine. Use a bowl with at least 3-cup capacity and a wide opening — not a tall mug — to allow steam to escape and prevent overflow.

Place bowl in microwave uncovered. Microwave on high 30 seconds to 1 minute, then stir to break up bubbles. Continue in 30-second to 1-minute intervals, stirring between each. Total time: ~2 minutes for instant oats, 3–5 minutes for rolled oats. Stay nearby — boil-overs happen fast near the end. Stir regularly to keep bubbles from surging.

Oats are done when they reach your desired consistency. If too thin, let sit 2 minutes at room temperature to thicken. Add toppings (fruit, nuts, syrup, nut butter, spices) just before serving. Don't overfill your bowl — oatmeal rises during microwaving. If it boils over, start fresh; burnt flavor infuses the whole batch and can't be fixed.