The past tense of Preheat is preheated.
verb. heat beforehand.
1. Verb, base form Once lit, close the lid and allow the grill to preheat for at least 10 minutes. 2. Verb, non-3rd person singular present And when you preheat your oven, give it an extra 10 to 15 minutes after it says it’s at the right temperature, just to make sure. 3. Noun, singular or mass Add oil to the skillet and preheat it over medium-high heat.