Heat oven to 375 degrees F.
In a skillet over medium-high heat, heat the oil. Add the spinach and cook until wilted. Add the pine nuts and cheese and stir to combine. Remove from heat and let cool.
Unfold the phyllo dough. Brush dough with some of the melted butter. Cut into strips about 4 inches wide. Place a damp paper towel or kitchen towel over the dough while assembling the spanakopita so that it doesn't dry out.
Place about 1 tablespoon of the filling on 1 end of the strip leaving about a 1-inch border from the bottom edge. Take 1 corner of the bottom edge and fold it over the filling to make a triangle shaped enclosure. Take the triangle and flip it onto the dough making another triangle fold. Continue to do this until the whole phyllo strip is used and the spanakopita is now formed into a triangular package. Repeat with remaining butter, filling and phyllo, (you may not need all of the phyllo dough).
Place all the spanakopita on a baking sheet and brush the tops with melted butter.