If you're doing oven appetizers, you'll want a stove top main course, and vice versa, so you aren't trying to juggle stuff in the oven when your guests are arriving.
With stuffed mushrooms, you could add marninated olives. Take plain green olives (pit in) and marinate with fresh rosemary, thinly sliced lemon zest, a bit of sliced garlic, fresh ground pepper and olive oil. Remove from the marinated, and warm before serving. Alternatively, you can gently warm the olives and seasoning in the oven, and serve directly.
If you want a non-oven appetizer course, the olives could still work (warm in the microwave). Brushetta would be good - thinly slice a day old baguette, brush with olive oil on both sides, and rub with a clove of garlic. Toast in a low oven until crispy. Top with finely diced fresh tomato, seasoned, or goat cheese and capers, or tapenade. You can do the bread ahead of time, but the tomato topping should be done shortly before serving.
If you want to continue the Italian theme, then you could go with lasagne as a main dish - spring for fresh noodles and a good sauce and assemble ahead of time (if you want, I've got an absolutely incredible recipe, but it does take some time). Serve with a simple salad of mixed greens with a vinagrette dressing, and a simple vegetable side dish or two. Then go for something refreshing for dessert to contrast the richness of the lasagne - say, lemon sorbet with fresh raspberries and coffee to go with.
