1/2 cup whole grain Dijon mustard
2 Tbsp olive oil
2 Tbsp butter (or margarine), melted
2 Tbsp fresh lemon juice
3 garlic cloves, minced
1 Tbsp dried oregano
1 tsp lemon peel
1 tsp kosher salt
3 lbs unpeeled red-skinned and white-skinned potatoes, cut into 3/4-inch wedges
Position 1 rack in top third of oven and 1 rack in bottom third of oven. Preheat to 425 degrees.
Spray 2 deep baking sheets (aluminum are good for quick clean-up). Whisk mustard, oil, butter, lemon juice, garlic, oregano, lemon peel, and salt in large bowl. Add potatoes. Sprinkle with freshly-ground black pepper and toss.
Spread potatoes in a single layer; roast 20 minutes. Rotate baking sheets in oven, turn potatoes, and cook until crispy on outside and tender on inside, about 25 more minutes.
Can be made 2 hours ahead of time. Let stand at room temperature. Reheat for 10 minutes.