I have a GE Range/Oven. Recently, when I turn on the oven to preheat, it trips my breaker in the house. My question is: would this be a problem with my oven (perhaps somekind of safety feature?) or with my electrical panel (because of the breaker blowing)?

It could be the breaker in the circuit panel. Sometimes they start tripping at lower current than they are rated at. Replacing the breaker is the fix.

However, it could also be a problem with the oven's heating element. It could actually be drawing more power than the circuit can handle. In this case, you would have to replace the heating element.

I'm trying to think of the best way to trouble-shoot this. If you have a clamp-on current meter, that would be the best test -- measure the current that the range is drawing. Unfortunately, it's not common that DIYers have them.

If you have an ohmmeter, you could disconnect the range from the wall and turn on the oven. Measure the resistance across the two power leads (not the neutral in the plug). That will give you an indication of how much power the element draws when it's cold.

I=\frac VR

where R is the resistance in ohms, V is the voltage (240 V), and I is the current.

Unfortunately, the element may have a resistance that's too low only when it's hot and this might not test that.

If you have another breaker of the same rating in the circuit panel, you could swap breakers and if the second breaker still trips, the oven is the problem. Otherwise, the breaker needs to be replaced.

I agree but want to bring it down a hair. Breaker blow for 2 reasons; they are over loaded, or they have become defective. Unless you know a great deal about working with 240 v I would suggest calling an electrician or appliance repair person. Right now we can't tell if it's the oven or the breaker but I do not want to encourgae you to open upo any electrical connections unless you have some experience, do you?

WHAT?. 220... 221? I guess I didn't mention, I'm not an electrician and I guess I should also mention, I'm a woman... not that there's anything wrong with that... and my husbands out of town working... Anyways, I guess I have a fifty fifty shot on calling in an electrician or an appliance repairer... Of course when I phone either of them... I get the same response... " Can't really say over the phone, I would have to come and look, Oh and that'll be $70 for the first 1/2hr" Arrggghhhh... Well thank you for your advise and responses.

How long after you switch the oven to clean does the breaker trip. If it trips immediately I would lean toward the oven being at fault. If it trips after some time I would tend to think weak breaker.
Can Hubby change out breaker? Maybe you should just stop cooking and cleaning until Hubby comes home. Take yourself out to dinner, you deserve it.