Cook artichokes according to package directions; drain. Cool slightly; coarsely chop. Preheat oven to 350°.
In a large skillet, heat butter and oil over medium-high heat. Add onion; cook and stir until tender. Add garlic; cook 1 minute longer. Stir in oregano and artichokes; remove from heat.
Sprinkle 1/4 cup Parmesan cheese into a greased 11×7-in. baking dish. Top with artichoke mixture.
In a large bowl, whisk eggs, milk, salt, pepper and nutmeg. Stir in Monterey Jack cheese and 1/4 cup Parmesan cheese. Pour over artichoke mixture.
Bake, uncovered, 30 minutes. Sprinkle with remaining Parmesan cheese. Bake until a knife inserted in the center comes out clean, 6-8 minutes longer. If desired, sprinkle with minced chives.