Yes, your prepped red potatoes should be fine in the fridge overnight. Since they are already cubed, oiled, and seasoned, they are ready for cooking, and keeping them in the fridge on aluminum foil will help maintain their freshness.

Here are a few tips to ensure they stay in good condition:

• Cover them well: Make sure the aluminum foil is tightly wrapped around the potatoes to prevent them from drying out or absorbing other flavors from the fridge.
• Storage: Place the wrapped potatoes in an airtight container or a resealable plastic bag for added protection.
• Temperature: Ensure your fridge is at or below 40°F (4°C) to keep the potatoes safe from bacterial growth.

When you're ready to cook them, you can either grill them as planned or use another method like roasting in the oven if the weather is still uncooperative.