Warms up ahead of time

• Starts the oven early
• Prepares an oven, as for baking
• Warms an oven
• Prepares an oven before baking
• Gives advance warming
• Prepares for cooking, as an oven
• Warms in advance
• Readies an oven
• Gets ready, as an oven

Wiktionary Word definitions in Wiktionary
vb. (en-third-person singular of: preheat )