I partially cooked a beef casserole this morning (about 8am) and left it in the oven to finish cooking between 4pm and 6pm tonight. Is this going to be OK? or will I make my family ill?
If it was cooked and stayed above 140 °F then you are fine.
If you just turned the oven off then it was probably below 140 °F for 2 hours and entered the danger zone. 90 °F to 140 °F food should not be left out more than 1 hour. Even then it is supposed to be fully cooked first. Is it safe - maybe? Definitely in the range for bad stuff to grow.
Below is from United States Department of Agriculture
"Danger Zone" (40 °F - 140 °F)
Leaving food out too long at room temperature can cause bacteria (such as Staphylococcus aureus, Salmonella Enteritidis, Escherichia coli O157:H7, and Campylobacter) to grow to dangerous levels that can cause illness. Bacteria grow most rapidly in the range of temperatures between 40 °F and 140 °F, doubling in number in as little as 20 minutes. This range of temperatures is often called the "Danger Zone."
- Keep Food Out of the "Danger Zone"
- Storing Leftovers
Keep Food Out of the "Danger Zone" Never leave food out of refrigeration over 2 hours. If the temperature is above 90 °F, food should not be left out more than 1 hour.
- Keep hot food hot — at or above 140 °F. Place cooked food in chafing dishes, preheated steam tables, warming trays, and/or slow cookers.
- Keep cold food cold — at or below 40 °F. Place food in containers on ice.
Cooking Raw meat and poultry should always be cooked to a safe minimum internal temperature (see graphic). When roasting meat and poultry, use an oven temperature no lower than 325 °F.
If you aren't going to serve hot food right away, it's important to keep it at 140 °F or above.
One of the most common causes of food-borne illness is improper cooling of cooked foods. Bacteria can be reintroduced to food after it is safely cooked. For this reason leftovers must be put in shallow containers for quick cooling and refrigerated at 40 °F or below within two hours.
Foods should be reheated thoroughly to an internal temperature of 165 °F or until hot and steaming. In the microwave oven, cover food and rotate so it heats evenly.