Are you eating because you're truly hungry, or because you're bored and used to filling in time with food?
You need to look at why the urge to overeat is there. Are you sad, happy, or bored? I am a boredom eater and constantly think I am hungry about an hour or so after eating, I would go and troll the cupboards and fridge constantly and end up walking away frustrated with myself because I didn't 'want' to eat and spoil everything so I'd walk away feeling dissatisfied, or I'd pick at something and walk away feeling disappointed in myself.
Eat a bigger meal as in more Low GI carbs, heavier in the protiens and fillers. Once you've finished then eating move away from the food area of your house compeltely. Also give yourself a time 2 hours after your main meal that you can have a snack. Plan what that snack is going to be, make it sound appealing, doesn't have to be naughty, but maybe do something up like a berry, yoghurt & museli parfait, or have a cup of low fat, low GI hot choc (milo) with some crackers and cheese, or fruit! If you find yourself looking at the clock constantly then remind yourself that you can eat at ....whatever time.... and that it'll taste all the better for waiting. Do the same after each meal. After about 2 weeks of doing this, by the time your snack time comes around you will eventually find that you're not really hungry after all, and will end up with a smaller snack to tide you over till lunch.
The other trick is to find alternative things to do to keep you busy in the meantime. Set yourself up a task that will have you busy for a while (The choices are endless!) get on the phone and talk to somebody, jump on the net and play some games (scrabble/bejewled are highly addictive), if you have Wii Fit get on there and muck about, or even if you just have a Wii play somebowling etc, do some gardening, get out and go for a walk, do some washing or tidy up. The list goes on and on. Make your time more constructive and you won't have the time for eating anymore.
It really does work!! It's just mind over matter.
Waiting for baby #4 to arrive then getting stuck into losing the 25kg that needs to come off!