Preheat oven to 375 degrees.
Place peeled and cut potatoes in a bowl and cover with cold water
Combine oil, lemon juice, garlic, salt, pepper and oregano and whisk well
Drain potatoes and place in a 9 x 13 baking/roasting pan
Pour dressing over the potatoes. Add fresh thyme and lemon slices if desired
Cover tightly with foil and carefully place in the oven on the bottom rack.
After 45 minutes give the potatoes a toss cover again and continue baking for another 30 minutes, remove foil and continue for 15 minute or until fork tender
If you want the potatoes to brown more at the end of cooking toss them in the reduced "sauce". If it's dry add a bit of olive oil, then place them under the broiler for a minute or 2 (only if you're using a metal pan). If you baked them in a non metal pan transfer before broiling